Volvo Bus(B9R) Gearbox

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Chassis ID Path
430/Description, Design and function//Gearbox
Model
B9R Identity
121019652
Publish date
12/12/08 ID/Operation

Gearbox
Contents

Overview gearbox EGS-V/EGS-VR
Type plate
Gearbox
Main components
Synchroniser
Range gearbox
Power flow
Compact retarder
Gear changing
Clutch pedal
Clutch servo
Lever assembly
Control unit
Emergency driving
Solenoid valve block
Control housing
Range cylinder
Gear shift cushioner
Lubrication system
Lubricating oil pump

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Overview gearbox EGS-V/EGS-VR

1. Gearbox
2. Compact retarder
3. Solenoid valve block
4. Control housing
5. Range cylinder with gear change cushioner
6. Clutch servo
7. Clutch pedal
8. Lever assembly
9. Control unit

The gearbox is installed vertically and has eight forward gears and one reverse gear in total. All forward gears are fully
synchronised. The gearbox is torque reinforced to be able to manage a maximum torque of 2000 Nm.

The gearbox is available in two versions, with or without retarder. The gearbox without retarder is designated EGS-V
and the gearbox with retarder is designated EGS-VR. The retarder version of the gearbox is combined with a new
compact retarder VR3250, integrated in the end housing. With the new compact retarder, the total length of the
gearbox is 92 mm shorter than the earlier retarder version.

The gearbox has a basic gearbox with four forward gears and a range gearbox which contains a planet gear with two
ratios, low range and high range. In high range, the power is transmitted directly to the drive wheels, and in low range a
gear reduction via the planet gear is obtained. The planet gear is engaged using the range cylinder. The range cylinder
is equipped with a gear change cushioner to make gear changing between low and high range quiet and soft.

The gearbox is disengaged using a hydro-pneumatic clutch servo. The clutch servo's piston rod is pressed forward by
hydraulic pressure assisted by compressed air. The piston rod movement operates the clutch release bearing. The

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

clutch servo is mounted with a bracket to the main housing on the gearbox.

The gear lever has no mechanical connection with the gearbox. Lever movement is transmitted to the gearbox through
an electro-pneumatic shifting system called EGS (Easy Gear Shift). A control unit processes the incoming signals from
sensors and decides if a gear change can be performed. The control unit sends signals to the solenoid valves that
control the pneumatically-operated pistons in the control housing and range cylinder. The piston affects the selector rail
which via the gear selector transfers the movement to the selector fork. The selector forks affect the synchroniser,
which couples the selected gear's gear to the main shaft. The input shaft is then directly or via a counter shaft coupled
to the main shaft. When the clutch is released the power transmitted by the engine passes through the gearbox and via
the cross-tooth coupling to the drive shaft.

Specifications:

Make Volvo

Designation EGS-V (gearbox without retarder)

  EGS-VR (gearbox with retarder)

Type Fully synchronised mechanical gearbox with an electro-pneumatic gear shift system.

Number of gears:

Forwards 8

Reverse 1

Gear ratio: Base gear Range gear Output gear ratio
Lever position at
program selection    (Input shaft:Output shaft)
2+ 7+  
RR  R Low range 13.69:1
11 
22  1 Low range 9.13:1
2+ 3  
34  2 Low range 6.42:1
45 
56  3 Low range 4.77:1
67 
7 7+   4 Low range 3.75:1

1 High range 2.44:1

2 High range 1.71:1

3 High range 1.27:1

4 High range 1.00:1

Dry weight:

Gearbox without retarder 260 kg

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by

the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Gearbox with retarder 345 kg

Length:

Gearbox without retarder 901 mm

Gearbox with retarder 912 mm

Total length:

Gearbox without retarder 994 mm

Gearbox with retarder 1025 mm

Oil change volume including filter 8.5 litres

Type plate

The gearbox is made by Volvo and is designated EGS-V for versions without retarder. Gearbox versions with retarder
are designated EGS-VR.

Explanation of designation EGS-VR:
E Easy
G Gear
S Shift
V Vertical (vertical installation)
R Retarder

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Gearbox

1. Clutch housing
2. Sensor G, gear engaged
3. Sensor N, neutral position
4. Control housing
5. Solenoid valve block
6. Main housing
7. Position sensor HR
8. Position sensor ROK
9. Range housing
10. Speed sensor
11. Range cylinder
12. Gear shift cushioner
13. Cross-tooth coupling
14. Output shaft
15. Planetary gear
16. Counter shaft
17. Main shaft
18. Input shaft

The gearbox consists of a clutch housing, main housing, range housing and control housing. The clutch housing and

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the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

main housing are made of aluminium. The main housing's lower part is cut so that the gearbox can stand vertically.
The range housing contains the range gear's planetary gear with shift mechanism and range cylinder. The planetary
gear is mounted together with the output shaft. The output shaft is journalled in ball bearings in the rear part of the
range housing.

Main components

1. Selector fork with selector bar gear 3/4
2. Selector fork with selector bar gear 1/2
3. Selector fork with selector bar gear R
4. Input shaft
5. Main shaft
6. Engaging sleeve
7. Gear base gear 3
8. Gear base gear 1
9. Gear base gear 2
10. Gear gear R
11. Counter shaft
12. Pump drive shaft
13. Reverse drive
14. Reverse shaft
15. Planetary gear
16. Output shaft
17. Cross-tooth coupling

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

The movement of the gear lever is transferred by the selector bars to the shift fork. The task of the selector fork is to
move the engaging sleeve forwards and backwards which via the synchroniser couples the selected gear's gear with
the main shaft. The shift fork for the 3/4 gear is rigidly fastened to the selector bar while the others have a jointed
fastening to each selector bar.

The input shaft, which transmits the engine power via the disc to the gearbox, is journalled in ball bearings in the clutch
housing. The input shaft always rotates clockwise. The input shaft gears are machined directly in the shaft. The power
is transmitted from the gear on the input shaft to the counter shaft. The input shaft can, with a synchroniser, be coupled
directly with the main shaft.

Both ends of the main shaft are journalled in roller bearings. Its front end is journalled in the input shaft and the rear
end in the main housing's rear end cover. The main shaft's gear is freely journalled with needle bearings and is coupled
to the shaft by the synchroniser.

The counter shaft is journalled in the clutch housing and the main housing's rear end cover. The counter shaft's drive
gear and the gear that drives the gear for the base gear three on the main shaft are pressed onto the shaft. The others
are machined directly in the shaft.

The reverse shaft is placed between a spacer sleeve in the main housing end cover and a bracket cast in the side of
the main housing. The reverse gear is journalled in needle bearings and has the task of changing the main shaft's
direction of rotation so that the vehicle can be reversed. The reverse gear is in mesh with the reverse gear's gear on
the main shaft and the corresponding gear in the synchroniser. When the reverse gear's gear is coupled to the main
shaft, the reverse gear changes the main shaft's direction of rotation which transmits the driving power via the output
shaft to the drive wheels.

The drive shaft for the lubricating oil pump runs through the reverse shaft. The pump drive shaft is journalled in a
needle bearing and is in constant mesh with second gear's gear on the counter shaft.

The material in all gears is reinforced and can withstand a maximum torque of 2000 Nm. All gears, except the reverse
gear, are helical gears which gives the gears a larger mesh area with each other and quieter running.

The flange is cross-toothed and is of the X-serration type XS 180. The companion flange has 4 bolts instead of the
previous 10.

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Synchroniser

1. Gear change fork
2. Engaging sleeve
3. Synchroniser cone
4. Clutch ring
5. Gear
6. Guide sleeve
7. Control plunge with spring
8. Main shaft

A Neutral position
B Synchroniser
C Gear engaged

The power from the engine is transmitted via the input shaft to the counter shaft. The counter shaft drives the main
shaft's freely journalled gear. The main shaft starts to rotate once its gear is coupled to the shaft. The synchroniser's
task is to adjust the speed between the freely journalled gear and the main shaft to later couple them together.

The synchroniser is a single synchroniser. The synchroniser comprises a guide sleeve which is coupled to the main
shaft with splines. Around the guide sleeve is an engaging sleeve meshed using spring-loaded control plunges. The
engaging sleeve's task is to move the synchroniser's cone towards the clutch ring and later to couple the guide sleeve

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16
with the gear.

Function:

A Neutral position
The engaging sleeve is held fixed in a centre position in relation to the guide sleeve by use of
spring-loaded control plunges. The synchroniser cone and the clutch ring's conical surfaces are
separated by an oil film. The main shaft's freely journalled gear with clutch ring rotate. The main shaft
does not rotate.

B Synchroniser
The gear change fork affects the engaging sleeve which presses the synchroniser cone towards the
clutch ring. Friction arises which makes the synchroniser cone and the clutch ring rotation speeds get
closer to each other.

C Gear engaged
When the rotating parts have reached the same speed, the engaging sleeve couples the guide sleeve
with the clutch ring. The gear is coupled with the main shaft and transmits the engine's power via the
output shaft to the drive wheels.

Range gearbox

1. Main shaft
2. Sun gear
3. Ring gear
4. Planet gear
5. Planet gear carrier

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by

6. the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

6. Output shaft
7. Engaging sleeve
8. Piston rod with selector fork

A High range position (released ring gear)
B Low range position (locked ring gear)

The range gearbox contains a planetary gear with two ratios, low range and high range. In high range, the power is
transferred directly to the drive wheels and in low range a down-change is obtained via the planetary gear. The
planetary gear is coupled via the range cylinder.

The planetary gear consists of five gears, so-called planet gears, which are in mesh with the main shaft's rear gear, the
sun gear. The planet gears are journalled in a planet gear carrier. Around the planet gears are the ring gears which are
coupled together with the engaging sleeve. The planet gear carrier and the output shaft are coupled together by
splines. The output shaft is journalled in a ball bearing in the end cover of the range housing.

The planetary gear's function:

The planetary gear is engaged and released by a pneumatically operated range cylinder that affects a selector
fork. The selector fork affects the engaging sleeve which is coupled to the ring gear.
In the high range position, the ring gear is released from the range gear housing. The planet gears are locked to
the planet gear carrier and the entire planetary gear rotates as one unit. The main shaft and the output shaft
then rotate at the same speed. Ratio 1:1.
In the low range position, the ring gear is locked to the range gear housing and the planet gears are forced to
rotate with the sun gear. The speed of the output shaft is then lower than the main shaft speed. Ratio 3.75:1.

When changing to high range position, the engaging sleeve is pressed towards the main shaft. When changing to low
range position, the engaging sleeve is pulled towards the output shaft.

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Power flow

1. Input shaft
2. Counter shaft
3. Main shaft
4. Gear, gear 1
5. Engaging sleeve synchroniser
6. Output shaft
7. Cross-tooth coupling
8. Planetary gear in low range position
9. Planetary gear in high range position
10. Reverse gear
11. Gear, gear R

The power is transmitted from the input shaft to the counter shaft, which then transfers the power to the gear on the
main shaft that is coupled by the synchroniser when the driver selects a gear. The input shaft can, by the synchroniser,
be coupled directly to the main shaft.

The gears on the main shaft rotate freely. When first base gear is engaged, the synchroniser locks the first gear's gear
to the main shaft. The power is transmitted from the input shaft to the counter shaft, and from there to the first gear's
gear on the main shaft. As the first gear's gear is locked, the power is transmitted to the main shaft. The power is
transmitted through the planetary gear, in both high and low range positions, via the output shaft to the cross-tooth
coupling.

The reverse gear is in constant mesh with the reverse gear's gear on the main shaft and the corresponding gear on the
counter shaft. When the reverse gear gear is coupled with the main shaft by the synchroniser, the reverse gear

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

changes the main shaft's direction of rotation. The main shaft now rotates counter-clockwise and the power goes via
the cross-tooth coupling to the drive shaft so that the vehicle can reverse.

Ratio: Base gear Range gear Output gear ratio
Lever position at
program selection    (Input shaft:Output shaft)
2+ 7+  
RR  R Low range 13.69:1
11 
22  1 Low range 9.13:1
2+ 3  
34  2 Low range 6.42:1
45 
56  3 Low range 4.77:1
67 
7 7+   4 Low range 3.75:1

1 High range 2.44:1

2 High range 1.71:1

3 High range 1.27:1

4 High range 1.00:1

Compact retarder

1. Incoming compressed air

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by

2. the Volvo Group

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

2. Control valve

3. Constant compressed air line

4. Oil sump

5. Filling duct

6. Restricted inlet

7. Rotor

8. Stator

9. Venting valve

10. Venting housing

11. Non-return valve, venting housing

12. Venting line

13. Restricted outlet

14. Cooling channel

15. Heat exchanger

16. Cooling water

17. Return channel from the heat exchanger

18. Oil temperature sensor

19. Coolant temperature sensor

20. Pressure sensor

In the retarder version, the gearbox is combined with a new compact retarder, VR3250. The retarder is a
hydro-dynamic brake and acts is a complement to the standard braking system to increase the service life of the wheel
brake linings. The retarder is built together with the planetary gear housing close to the output shaft that drives the rotor
shaft's gear. The retarder only affects the drive wheels. The retarder has no braking effect when stationary or with
slowly turning wheels. Consequently it cannot be used as a parking brake or to block the wheels.

The retarder can be engaged with the brake pedal or with a hand lever operation. When the brake pedal is depressed,
the brake pedal potentiometer gives a continually increasing application level in proportion to the pedal angle. Full
application level is obtained at about a 9° pedal angle. The lever must be in position A to enable pedal application.

Constant speed braking can be obtained by pressing the toggle switch ± when the lever is in the A position. The
current speed is stored in the Vehicle Electronic Control Unit (VECU) as a braking constant speed until the lever is
moved from the A position. During braking, the set speed can be finely adjusted by pressing + or -. On buses equipped
with a cruise control this also controls the engagement of the retarder. The retarder is activated should the set speed
be exceeded by 7 km/h when driving downhill. This basic speed value of 7 km/h can be changed by the toggle switch ±
to a value between 4 to 15 km/h. The value is shown in the display for 5 seconds after the selection is made.

All analogue controls are connected to the Vehicle Electronic Control Unit (VECU) which converts the selected lever
position to a digital signal for the desired application level which is sent to the retarder control unit (RECU). The control
unit orders the control valve, connected to the bus pneumatic system, to supply controlled/adjusted air pressure to the
oil sump. A certain amount of oil in the sump is pressed through a filling duct via a restricted inlet to the retarder
working space between the rotor and stator. At the same time as oil is filled, the air in the retarder must be forced out
through the air vent valve. When the oil reaches the valve ball, the ball will rise and close the outlet to the air vent
valve. The stator is fastened in the retarder housing. The retarder is pressed onto the rotor shaft which is gear-driven
by the gearbox's output shaft. The rotor vanes set up a braking oil flow through the stator vanes. The amount of braking
torque obtained from the oil flow depends on the amount of oil in the retarder space and the speed of the rotor. The
maximum braking torque built up at full application is dependent on speed and reaches its maximum at a propeller
shaft speed of approx. 1000 rpm when the dynamic pressure is at minimum 18 bar.

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

The inertia used is entirely converted to heat energy and to prevent the retarder from overheating, some of the working
oil must continually flow through the heat exchanger. A restricted outlet in the cooling channel controls the oil flow
through the heat exchanger. When application ceases (idling), the pressure in the control valve is evacuated through
the air vent pipe and opens the non-return valve in the air vent housing. As the oil in the retarder begins to sink back to
the sump, the air vent valve opens so that rapid draining is obtained. To reduce the energy losses in the stator when
the retarder is at idle, there are special interruption channels which interrupt the air flow so that no braking air flow
arises.

The retarder control unit is integrated in the bus electronic application BEA. The retarder's function and working
condition are monitored by the retarder control unit by means of two temperature sensors, one for oil and one for
coolant, and by a pressure sensor which confirms that applied pressure conforms with commanded application level to
the control valve. The control unit also receives position signals from, among others, the accelerator pedal, the speed
sensor, engine speed and the ABS system. Signal communication over data links enables direct interaction with other
functions that affect brake application such as exhaust brake, cruise control and ABS system. The instrument panel
display shows which application step is selected and a warning message, and allows fault messages to be read.
Fault-tracing and component checks can be done using the VCADS Pro tool.

When there is a tendency to overheat, the control unit activates a deregulating function that gradually reduces the
application until the retarder has cooled down to its normal operating temperature. The yellow control lamp INFO and a
display symbol inform the driver of reduced braking torque during active deregulation. The retarder application will
cease if the driver presses the accelerator pedal. The signal for active ABS system will also stop the application.

Specifications: 3250 Nm
Max. braking torque
Application: 0 Completely disengaged retarder function
Hand lever, six positions A Supply pedal application and auto position for cruise control braking
  ± Toggle switch for regulating cruise control
  1-4 Fixed application steps
  2.65 ± 0.10 bar
Application pressure sump full
application 1 5% (Including exhaust brake, 25 %)
Braking effect in % per step 2 35 % (Including exhaust brake, 50 %)
  3 70 % (Including exhaust brake, 75%)
  4 100 % (Including exhaust brake, 100%)
 

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Gear changing

1. Lever assembly
2. Position sensor, clutch pedal
3. Clutch pedal
4. Control unit
5. Cover DIP switch
6. Sensor G, gear engaged
7. Sensor N, neutral position
8. Control housing
9. Solenoid valve block
10. Reversing light switch
11. Range cylinder with gear shift cushioner

The gear lever has no mechanical contact with the gearbox. Only a gear shift request is obtained using the gear lever.
Lever movement is transmitted to the gearbox through an electro-pneumatic shifting system called EGS (Easy Gear
Shift). Seven of the gearbox's eight forward gears are engaged by moving the gear shift lever to each gear position.
The eighth gear is engaged using the plus button in the gear shift knob. A control lamp lights with a steady light when
the plus button is operated.

A program selection controls which gear is to be engaged when the plus button is operated. There are two programs, 2
+ and 7+. With program 2+ set, third gear is engaged with the plus button. With program 7+ set, eigth gear is engaged
with the plus button. The gear shift program is set using the control unit's DIP switch. At delivery, gear change program
choice 7+ is pre-set.

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Gear ratio: Base gear Range gear Output gear ratio
Lever position at
program selection    (Input shaft:Output shaft)
2+ 7+  
RR  R Low range 13.69:1
11 
22  1 Low range 9.13:1
2+ 3  
34  2 Low range 6.42:1
45 
56  3 Low range 4.77:1
67 
7 7+   4 Low range 3.75:1

1 High range 2.44:1

2 High range 1.71:1

3 High range 1.27:1

4 High range 1.00:1

The lever movement affects a number of micro-switches, one for each gear. The control unit processes the incoming
signals from, besides the micro-switches in the lever assembly, also signals from the clutch pedal position sensor, gear
position sensor, tachometer and two speed sensors. The gearbox position sensor is of the contact type, either a closed
circuit or an open circuit. The are four such position sensors:

Neutral (N)
Gear in basic gearbox engaged (G)
High range position (HR)
Range gear engaged (ROK)

The control unit decides if gear changing can take place and performs a gear change. The control unit then sends
signals to the solenoid valves in the lever assembly's pneumatic cylinder and to the solenoid valves controlling the
control housing's and range cylinder's pneumatically operated pistons. These pistons engage and disengage the base
gears and the planetary gear.

Driving:

When the engine is started the EGS diagnostics lamp will light for approx. one second. During this time the EGS
system performs a self-test. If the lamp does not go out after this second, or comes on while driving, there is a serious
fault in the system. In most cases, the gearbox cannot change gear.

The engine must be running and the clutch pedal fully depressed before a gear can be engaged. When changing down
at high speed, especially when skipping one or more gear positions, the gear lever will lock in neutral temporarily to
protect the gear shifting system from overspeeding. Using this overspeed protection on a regular basis will cause
abnormal wear to the gearbox controls and synchronisers and should therefore be avoided.

The reverse gear and first gear are blocked and can be engaged only if the locking ring is lifted up towards the gear
lever knob. First gear is used when marshalling and starting on steep inclines.

When the plus button is pressed down a symbol is shown in the display. The gear is engaged once the clutch pedal is

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

depressed and then released again.

Gear shift function:

As an example, shifting from fourth to fifth is explained (selected program 7+, base gear 4 LR to base gear 1 HR). In
this gear shift step the planetary gear is also changed, which in principle is the only difference compared to other gear
shift steps.

1. The driver presses down the clutch and moves the lever from gear position four to the neutral position.
A completely depressed clutch pedal sends a low signal (approx. 0.7 V) to the control unit. The lever assembly's
micro-switch for fourth, moves to the neutral position (rest position). The control unit then registers neutral in the
lever and activates the neutral solenoid valve, which supplies air between the pistons in the gearbox control
housing. The gear lever solenoid valve activates the interlock cylinder. Sensor G (gear engaged ) opens, and
sensor N (neutral position) closes.

2. The clutch is held depressed and the lever is moved from neutral towards gear position five.
This position means that fifth gear is requested at the control unit. The control unit then activates solenoid valve
HR. As long as gear change is ongoing, sensor ROK is open. Sensor HR closes, and thereafter sensor ROK
closes. In earlier versions of the system, the gear shift lever was locked by the interlock cylinder for a few
moments when the gear shift lever was moved to the next gear.

3. The lever is moved into the gear position five and the clutch is released.
Sensor G closes. The voltage to solenoid valve neutral is disconnected and the solenoid valve vents. The
voltage to the gear shift lever's solenoid valve is disconnected and the lever's interlock cylinder is vented. The
lever can then be moved on to gear position five. On later versions of the control unit, the gear shift lever is
released by the interlock cylinder at the same time as the base gearbox gear is engaged.

Parking:

Even though the gear lever can be moved to a gear position when the engine is shut off, this does not mean that a
gear is engaged in the gearbox. Therefore, the handbrake must always be applied when parking. A buzzer will sound if
the engine is turned off without the handbrake being applied.

Copyright to this documentation belongs to the Volvo Group. No reproduction, copying, change, amendment or other similar disposal is entitled without prior written consent by
the Volvo Group

The information contained herein is current at the time of its original distribution, but is subject to change. The reader is advised that printed copies are uncontrolled.

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IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Clutch pedal

1. Pedal assembly
2. Clutch pedal
3. Master cylinder
4. Hydraulic lines
5. Position sensor
6. Clutch fluid reservoir
7. Micro-switch, cruise control

The gearbox is disengaged using a hydro-pneumatic clutch servo. When the clutch pedal is depressed, a hydraulic
pressure is created in the pedal assembly's main cylinder. The pressure is transferred via a hydraulic line to the clutch
servo which is mounted on the gearbox. The clutch servo's piston rod is pressed forward by hydraulic pressure

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18 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

assisted by compressed air. The piston rod movement operates the clutch release bearing.

Function, position sensor clutch pedal:

1. The clutch pedal is pressed down.
2. A metal plate on the clutch pedal passes an inductive position sensor fitted in the lever assembly.
3. The position sensor reacts and sends a low signal to the control unit. The control unit senses the changed signal

and registers that the gearbox is disengaged and that a gear change is in progress.

Clutch servo

1. Clutch servo
2. Hydraulic line connection
3. Control cylinder
4. Vent nipple for hydraulic system
5. Reaction plunger
6. Compression spring
7. Control valve
8. Air chamber
9. Compressed air connection
10. Air cylinder
11. Compressed air piston
12. Air channel with air outlet
13. Piston rod
14. Air passage

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15. the Volvo Group

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19 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

15. Draining channel

The clutch servo system is a hydro-pneumatic system. The clutch servo's piston rod is pressed forward by a hydraulic
pressure assisted by compressed air. The piston rod movement operates the clutch release bearing. The clutch servo
is mounted with a bracket to the base housing in the gearbox.

Function, clutch servo:

1. The clutch pedal is pressed down and creates a hydraulic pressure in the main cylinder at the clutch pedal.
2. The hydraulic pressure is transferred via a hydraulic line to the control cylinder.
3. The hydraulic pressure increases in the control cylinder and presses the reaction plunger against the control

valve.
4. The control valve opens and releases compressed air into the air cylinder. The compressed air piston is pressed

forward until the clutch pedal is completely depressed. The compressed air is also led from the air cylinder
through the air channel in the reaction piston and control valve to the air chamber. The increased pressure in the
air chamber presses the control valve against the reaction piston so that air cannot be evacuated through the
reaction plunger's air channel.
5. The compressed air piston reaches its end position and the hydraulic pressure in the control cylinder stabilises.
The higher pressure from the incoming compressed air pushes back the control valve and reaction plunger. The
control valve shuts off the air supply. The reaction piston still seals against the control valve. The compressed
air piston is held in the same position by the hydraulic pressure against the piston rod in the control cylinder.
6. When the clutch pedal is released, the hydraulic pressure in the control cylinder drops. The pressure spring
pushes back the reaction piston which parts from the control valve and the reaction plunge's air channel to the
air outlet opens.
7. The compressed air piston is pressed back by the clutch lever spring and the air cylinder is emptied of air via the
reaction plunger's air channel to the air outlet with silencer. To prevent negative pressure in the air cylinder, and
dirt from being sucked in, the air is led from the air outlet via an air passage to the space in front of the
compressed air piston.

Disengaging without compressed air:

The clutch functions even when compressed air is not available. The clutch then functions as a hydraulic clutch but will
be stiff to operate as there is no compressed air, and therefore has no servo assistance.

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20 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Lever assembly

1. Lever assembly
2. Gear lever
3. Gear lever knob
4. Interlock cylinder
5. Interlock cylinder solenoid valve
6. Emergency driving switch
7. Emergency driving switch
8. 35 pin contact
9. Circuit board with micro-switch
10. Sliding sleeve

The lever assembly's gear lever requests a gear change. Not until the control unit has received complete information

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21 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

from its sensors will it engage the requested gear. The gear lever is prevented by the interlock cylinder from moving to
its end position before the gear is engaged.

Interlock cylinder function:

1. In neutral position there is compressed air between the two cylinders in the interlock cylinder, which makes the
lever feel as if it is locked and can only be moved half its travel distance.

2. When the gear lever is moved towards the gear position, a sliding sleeve affects a micro-switch that informs the
control unit which gear is to be engaged.

3. The control unit gets information from position sensor G that a gear is engaged. The control unit disconnects the
voltage to the interlock cylinder's solenoid valve, and then the space between the pistons in the interlock cylinder
is vented. The lever can now be moved the entire distance. A pawl keeps the gear lever in its end position.

A built-in fault diagnostics system registers faults that occur in the electrical system. When the diagnostics switch in the
lever assembly is used, a fault code is shown via a diagnostics lamp in the instrument panel that flashes at different
intervals.

The diagnostics program is activated by the diagnostics switch in the following way:

1. Turn the starter key to the drive position.
2. With the gear lever in neutral and the bus stationary, press the lower part of the diagnostic switch.
3. A fault will be indicated by the diagnostic lamp flashing at two different intervals resulting in a fault code. Slow

flashing intervals indicate the fault code in tens and a fast flashing interval in ones. Example: one slow and one
fast flash give fault code 11, two slow and three fast flashes give fault code 23.
4. Check if further faults are stored by pressing once more on the diagnostic switch. If there are more fault codes
stored, these are shown. Repeat the procedure unit the first fault code is repeated.

Fault codes are grouped as follows:

11 - 13 Service information
21 - 45 Faults concerning the gearbox
56 Faults which concern the disengagement sensor
61 - 66 Faults affecting engine speed, vehicle speed and lever assembly

Once the fault has been rectified, the stored fault codes are deleted as follows:

1. Turn the starter key to "0" position.
2. Press in the diagnostic switch and hold it depressed while the starter key is turned to drive position.
3. Wait until the diagnostic lamp gives two short flashes and one long (after 2 seconds).
4. Release the diagnostic switch.

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22 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Control unit

1. Control unit
2. Cover for DIP switch
3. 35 pin contacts
4. Emergency driving board

A Program 2+

B Program 7+

The control unit is the main unit and comprises two circuit boards; one for signal processing and drive steps, and one
for the software. The control unit processes signals from the lever assembly's micro-switches, rev counter, tachometer
and the clutch pedal position sensor, and four other position sensors. As a security measure, the control unit also
receives a signal from the tachometer sensor on the gearbox.

The drive stage contains transistors that send signals to the lever assembly's solenoid valve for the interlock cylinder,
and to the solenoid valve block on the gearbox. A change in the control unit's software makes gear changing faster.

In order for a gear to be engaged, the engine speed must be higher than 300 rpm. The speed limit for gear changing
from third to second is 2200 rpm. For other gears, the limit is, as previously 2800 rpm. If the engine is switched off with
a gear engaged, the control unit will engage neutral position. It is not possible to park the bus with a gear engaged.

Should a gear be engaged when the gear lever is in neutral, the control system will detect the fault and light the
warning lamp together with the central warning lamp and activate the buzzer. In this position the engine cannot be
started unless the clutch pedal is depressed and the clutch sensor activated. The warning lamp, central warning lamp
and the buzzer are also activated if a pre-selection of a gear is done while driving.

If a fault occurs on sensor G and the speed exceeds 5 km/h, the control unit will not engage neutral in the gearbox. The
fault is not noticed until the next gear change. The interlock cylinder then locks the gear lever in neutral and the
warning lamp is lit together with the central warning lamp and the buzzer is activated.

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23 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

If a fault occurs on sensor G and the speed is below 5 km/h, the control unit will put both gearbox and gear lever in
neutral. The interlock cylinder will prevent the gear lever from moving to its end position. The gear lever must be held in
its current position to keep the gearbox engaged until the speed exceeds 5 km/h.

The control unit should be placed in a protected place where it is easily accessed. The control unit is not fused and has
diodes as protection against voltage peaks. It is also protected againt pole reversal. The two 35 pin contacts have
different colours to avoid interchange.

The EGS system has an emergency driving system built into the control unit.

The EGS system has two gear changing programs. The selected program controls which position the gear lever has
for each gear engaged. Program selection is done using the DIP switches, which are located under a cover in the lower
part of the control unit.

Setting for program 2+

A Button 1 2 3 4 5 6 7 8

  Position Off On Off Off On Off Off Off

Setting for program 7+

B Button 1 2 3 4 5 6 7 8

  Position Off On Off Off On Off Off On

Gear ratio: Base gear Range gear Output gear ratio
Lever position at
program selection    (Input shaft:Output shaft)
2+ 7+  
RR  R Low range 13.69:1
11 
22  1 Low range 9.13:1
2+ 3  
34  2 Low range 6.42:1
45 
56  3 Low range 4.77:1
67 
7 7+   4 Low range 3.75:1

1 High range 2.44:1

2 High range 1.71:1

3 High range 1.27:1

4 High range 1.00:1

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24 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Emergency driving

1. Lever assembly
2. Emergency driving switch

The EGS system has an emergency driving system built into the control unit.

A symptom that there is a fault in the gearbox electrical system or control unit can be the diagnostic lamp being lit
constantly. The fault can be overridden temporarily by activating the built-in emergency driving system using the
emergency driving system switch located on the lever assembly.

Function, emergency driving system:

1. The bus must be stationary with the engine running. With the engine running one does not risk a voltage drop
during the starting sequence which would deactivate the emergency driving system.

2. Press the emergency driving switch. The diagnostic lamp in the instrument panel flashes.
3. Depress the clutch pedal.
4. Hold the clutch pedal depressed and engage an available gear. Available gears are in lever positions 1 - 5 and

R. Other gears are locked.
5. Release the clutch.

Gear changing will be slower than normal because of the electronic monitoring system being partly out of function.
Emergency driving cannot be disengaged while the engine is running and, if it is still required, it must be re-engaged
each time the engine is started.

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25 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Solenoid valve block

1. Solenoid valve base gear 1
2. Solenoid valve base gear 2
3. Solenoid valve base gear 3
4. Solenoid valve base gear 4
5. Compressed air connection HR
6. Compressed air connection LR
7. 10 pole connection piece

N Solenoid valve neutral
R Solenoid valve - reverse gear
HR Solenoid valve HR (High Range)
LR Solenoid valve LR (Low Range)

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26 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

All solenoid valves are collected in one solenoid valve block. The solenoid valves control the air flow to the control
housing and the range cylinder. The control housing controls gear positions N, R, 1, 2, 3 and 4. The range cylinder
controls the planetary gear positions HR (high range) and LR (low range).

All solenoid valves are normally closed and get no positive voltage from the control unit if the clutch pedal is not
depressed. If the power supply is broken, the gearbox will retain the engaged gear.

When the bus stops and the electrical power is disconnected with the starter switch (+15) a so-called reset function
takes effect. The neutral valve's voltage supply is maintained until the system has set the gearbox and gear lever to the
neutral position.

The solenoid valve block has a new connecting piece with a 10 pole contact:

Pin / Contact Solenoid valve / Gear
B N
H R
D 1
E 2
A 3
F 4
G LR
C HR
I - (Plugged)
J Power supply, +24V

Technical data, solenoid valve block:

Nominal size Valve 1-8, diameter 4 mm

Operating pressure 2.0 bar to 10 bar

Valve seat sealing Viton

Temperature range: -40°C to +100°C

Built-in position Independent

Voltage range 24 VDC

Holding voltage min. 10 VDC

Output 5W

Connection time 100 %

Valve housing material Aluminium

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27 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Control housing

1. Sensor N, neutral position
2. Selector rail, base gear 3/4
3. Selector rail, base gear 1/2
4. Selector rail, base gear R
5. Balls for signal to sensor G
6. Gear selector
7. Control cylinder, base gear 1/2
8. Control piston
9. Control cylinder, base gear 1/2
10. Control piston, reverse gear
11. Solenoid valve, gear N
12. Control piston, base gear 4
13. Control cylinder, base gear 3/4
14. Control piston, base gear 2
15. Control piston, base gear 3
16. Control piston, base gear 1
17. Selector rail lock
18. Selector rail washer
19. Solenoid valve base gear 1
20. Sensor G, gear engaged
21. Solenoid valve base gear 2

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28 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

A Neutral position
B Changing to first gear's base gear
C Changing to second gear's base gear

The control housing has three selector rails. On each selector rail there is a gear selector which transfers the
movement to the gear change fork. The selector rail's direction of movement depends on which control piston in the
control cylinder is pressing on the selector rail's washer. The solenoid valves control the compressed air, which affects
the control piston in the control cylinder.

A In neutral, compressed air is supplied to the space between the control pistons in all control cylinders,
which locks the selector rails. The control cylinder for reverse gear is constantly vented when there is
no crawl gear function.

B When first base gear is selected, compressed air is supplied behind the control piston for base gear 1 at
the same time as the space between the pistons is vented through the neutral position's solenoid valve.
The control piston presses on the selector rail and first base gear is engaged. When the gear is
engaged, the control cylinder is vented.

C When changing from first gear's base gear to second gear's base gear, air is supplied to the space
between the pistons and the selector rail moves to the neutral position. Then compressed air is supplied
behind the control piston for base gear 2 at the same time as the space between the pistons is vented
through the neutral position's solenoid valve. The control piston presses on the selector rail and second
gear's base gear is engaged. When the gear is engaged, the control cylinder is vented.

The selector rail lock prevents two gears from being engaged at the same time. When a selector rail leaves its neutral
position, the balls are moved which lock the other selector rails.

The control housing has two position sensors, N (Neutral) and G (Gear engaged). The sensors have two positions,
closed or open circuit. Sensor N indicates to the control unit that the gearbox is in neutral and gear changing can
continue. Sensor G indicates that changing has been completed and the control unit sends a signal to the lever
assembly's interlock cylinder that the gear lever can be moved to the end position.

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29 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Range cylinder

1. Gearbox housing
2. Position sensor HR
3. Range housing
4. Position sensor ROK
5. Piston rod
6. Selector fork
7. Range cylinder
8. Incoming air, low range
9. Incoming air, high range
10. Piston rod, gear change cushioner

The range cylinder affects a selector fork which via the clutch sleeve engages and disengages the range gearbox's
planetary gear. When changing to high range position, the selector fork is pressed towards the gearbox housing. When
changing to low range position, the selector fork is pressed in the opposite direction.

The range cylinder has two position sensors, HR and ROK. Position sensor HR is activated by the cylinder piston rod
and indicates that the planetary gear is in the high range position. Position sensor ROK indicates when gear changing
is done in the planetary gear, and thereby changing is prevented in the main gearbox. ROK keeps the circuit open as
long as changing of the range gear is ongoing and closes when one of the range gears is engaged. Position sensor
ROK must be adjusted when installing.

Adjustment of range cylinder:

Before the selector fork reaches its stop in the synchroniser, the distance between the piston and the range cylinder
cover should be 0.35-0.85 mm. Adjustment is done with adjuster shims. In the retarder versions, the adjuster shims are

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30 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

placed on the cover, and in versions without retarder the adjuster shims are placed on the piston.

Adjusting the sensor ROK:

1. Shift the range cylinder to low range using compressed air.
2. Fit the sensor without shims.
3. Connect a buzzer to the sensor.
4. Screw in the sensor until the buzzer is silent, then screw out the sensor until the buzzer sounds again.
5. Measure with a feeler gauge between the sensor and housing. Note the measured value.
6. Using compressed air, change the range cylinder to high range and make the corresponding measurements.

Use the largest measurement value and add 0.8 -1.2 mm. Choose as few adjuster shims as possible.

Gear shift cushioner

1. Range cylinder
2. Gear shift cushioner
3. Silicone oil
4. Lock ring

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5. the Volvo Group

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31 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

5. Rubber container for compensation volume
6. Piston rod bushing
7. Cushioner housing
8. Cylinder liner
9. Piston with piston rod
10. Channel for pressure equalisation
11. Draining channel
12. Wiper for oil
13. Piston rod seal
14. T-groove coupling

A Start position:
B Cushioning has started
C Position when the gear engages

The range cylinder is equipped with a gear change cushioner to make gear changing between low and high range quiet
and soft. The cushioner works with silicone oil and brakes the gear change movement just as engagement takes place,
and therefore does not affect the changing time. The cushioning function is the same when changing from low range to
high range and vice versa.

Function:

A Start position (High range position)
The silicon oil flows out through the holes in the middle of the cylinder liner.

B Cushioning has started
The piston has been moved and covers the centre holes. Oil flows out through a hole further along in
the cylinder liner and a hole in the piston.

C Position when the gear engages (Low range position)
The piston has been moved some more and now covers the inner hole in the cylinder liner. The
movement is braked by the remaining oil now being forced out through the hole in the piston.

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32 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Lubrication system

1. Oil filter
2. Lubricating oil pump
3. Reverse gear
4. Pump drive shaft

The gearbox is partly lubricated by pressure, partly by splash. The input shaft's, main shaft's and planetary gear's
bearings are pressure lubricated by a built-in lube oil pump.
The pump sucks oil from the lowest point in the gearbox through a collection pipe. The lubricating oil is then pressed
through the oil filter and on to a grooved spacer ring on the main shaft, which seals against the cover with two piston
ring seals. The oil is led through channels in the main shaft into the oil distribution pipe.
The oil distribution pipe is screwed at the middle of the main shaft's rear. The most important lubrication points are the
planetary gear and the conical roller bearings. The planetary gear is lubricated by oil passing through four small holes
and sprayed onto the planetary gear. The counter shaft and reverse gear are splash lubricated.
The lubricating oil pump is fitted on the rear casing of the gearbox and is driven by a drive shaft which is in constant
mesh with second gear's gear on the counter shaft.
The replacement volume is approx. 8.5 litres.

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33 / 34

IMPACT 4.00.51.00-SNAPSHOT 01/03/16

Lubricating oil pump

The lubricating oil pump is of the pump ring type with an eccentrically placed rotor. The lubricating oil pump is driven by
a drive shaft which is in constant mesh with second gear's gear on the counter shaft. The drive shaft goes through the
rear shaft and journalled with a needle bearing at each end. The pump is equipped with a reduction valve (3) which
limits the lube oil pressure and another reduction valve (2) which opens when the lubricating oil filter is clogged.
The oil pump sucks oil from the sump and pumps the oil through the filter (1). The oil from the oil pump passes through
two overflow valves, that of the filter and that of the oil pump. The filter's overflow valve opens when the filter is clogged
or when the oil is more viscous, for example when the oil is cold.

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34 / 34