Replacing the DYNA VT unit


Disassembling the Dyna VT module

Drain the transmission oil (approx. 65l). Disassemble the cab.
Remove the unions after emptying, taking the precautions necessary to prevent any dirty particles from entering the air conditioning circuit Pinch the heating pipes closed to avoid draining the circuit. Attach the cab to a suitable hoisting system and lift it off. Disconnect the cables and hydraulic unions, taking care to mark them. Remove the spool valve block. Hoist and remove the cab. Remove the accumulator assembly. Move the range selector to neutral. Take off the limp home console. Disconnect the connector.
Remove the control unit. Take off the pressure filter housing. Recover the oil that flows out. Remove the electrical connectors and hydraulic pipes. Remove the valve block. Disconnect the connectors, the clutch vent line and the hydraulic pipes. Remove the valve block. Disconnect the electrical connector and remove the summing shaft sensor. Remove the pipe support and strapping. Unscrew the cover screws.
Raise the cover using the M10 eye-bolt. Unscrew the locking screw and take out the control shaft. Remove the retainer circlips and push the hoses inwards. Disconnect the high pressure hoses. Remove the 3 circlips and push the hoses inwards. Remove the hydraulic pipes (supply pressure of auxiliary functions). Take off the drive shaft circlip. Push the shaft backwards.
Unscrew the 3 M8 screws from the planet carrier. Push the shaft backwards.
Remove the drive pinion circlip. Push the circlip, washer and socket towards the drive pinion, as indicated by the arrow. Swivel the hydrostatic motors and the pump inwards using a lever. Unscrew the 2 nuts located on the left and right. Unscrew the upper M12 locking screw.
On the inner surface of the gearbox housing, unscrew the 2 closing plugs.
Recover the oil. Unscrew the 2 locking screws on the lower shaft. Install lifting tackle. Slightly raise the hydraulic module, ensuring the lifting tackle remains under a certain level of tension. Using a slide hammer puller on the M20 threads, extract the flexible suspension shafts. Take the transmission module carefully out of the gearbox housing using the lifting tackle. Stay alert in case other parts move.

Assembling the Dyna VT module

Raise the transmission block with lifting tackle, after securing it.


Move the range selector (Hare / Tortoise) (arrow) to “Neutral” (middle position). Clean any oil or seal fragments from the transmission housing mating face. Move the range selector finger to “Neutral”. (middle position). If necessary:
Fit the circlip and washer on the shoulder of the drive pinion.
Push the socket onto the drive pinion.
Fit the flange on the link shaft (PTO drive) and fit the link shaft.
Fit the transmission module in the transmission housing. Stay alert in case other parts move.
Fit the two shafts into the bores of the transmission housing and transmission module. The two shafts are of different lengths; the longer one is fitted at the base of the gearbox.
Check the sockets (flexible) for wear, and fit new sockets if necessary. Insert the sockets home into the bores. Fit the ring, with the bore turned towards the flexible socket. Tighten the M20 nut. Carry out the same assembly operation on the three other threads. Tighten the four M20 nuts to a torque of: 250 Nm. When tightening, hold the opposite nut still. Unhook the lifting tackle. Install a planet gear of the power transmission epicyclic gear train turned upwards.
Centre the transmission module. The distance between the ring gear and the transmission housing must be identical on either side. Tighten the 4 locking screws to a torque of: 86 Nm. Install 2 closing plugs fitted with new seals under the transmission housing. Test the correct operating of Hare / Tortoise range shifting (check finger positioning). Turn the transmission module until a tooth of the disc, intended for the Hall sensor, can be seen at the middle of the bore. (arrow).


Smear the mating face of the Hall sensor with sealing product (ref. X903.050.553) (non-hardening) and insert the sensor into its housing.
Tighten the attachment screws to a torque of: 25 Nm. Reconnect the electrical connector. If the Hall sensor is being reused, insert 2 strips of paper 0.9 mm thick into the Hall sensor groove (these strips ensure centring). Swivel the hydrostatic motors to their stop (45°). Pull the drive pinion socket forwards to release the groove from the circlip. Insert the circlip into the groove. If the socket does not engage, chock a front wheel and turn it until the socket is engaged. Fit the flange on the epicyclic gear train. Tighten the M8 screws to a torque of: 25 Nm.
Insert the hydraulic hoses into the bores on the front right-hand side of the transmission housing. Secure the hoses using circlips (opening facing downwards).
- 1 = short blue hose (flushing)
- 2 = long blue hose (boosting)
- 3 = black hose (lubricating)
At the front on top of the transmission housing:
Fit the ring in the groove of the shaft.
Push the shaft forwards. Install the washer.
Fit the circlip in the pinion groove.
Fit the hydraulic pipe (supply pressure of auxiliary functions).
Insert the pressure pipes in the bores in the right-hand side of the transmission housing.
- 1 = supply pressure hydraulic hose
- 2 = Hare range shifting
- 3 = ground speed limiting
- 4 = Tortoise range shifting
- 5 = Regulating valves (tilting)
- 6 = High pressure for forward clutch and coupler function.
Attach the hydraulic pipes using circlips. Screw 2 M8 threaded rods into the transmission housing. Fit new O’rings. Stick seals in the block using grease.
Fit the control block. Tighten the attachment screw (from the inside to the outside) to a torque of: 25 Nm.
Connect the connectors, clutch function bleed pipe and hydraulic pipes.
- 4V1 = Hare range solenoid valve
- 4V2 = Tortoise range solenoid valve
- 4V4 = Coupler function solenoid valve
- 4V3 = Ground speed limiting solenoid valve
Screw 2 M8 threaded rods into the transmission housing. Fit new seals. Fit new seals with grease in the valve block. Install the block and tighten the screws, starting with the inside screws to the following torque: 25 Nm.
Connect the connectors and hydraulic pipes. Fit new O’rings with grease and attach the pressure filter, tightening the screws to the following torque: 25 Nm. Connect the connector. If necessary, smear the lip seal with a mixture of white spirit and water (1:1) and fit it home. Fill the lip seals 2/3 full with grease. Fit the control shaft. Turn the shaft until the locking screw thread can be seen. Smear the thread of the Allen screw with plastic binder and tighten the screw to the following torque: 25 Nm.
Fit the intermediate coupler with the two bosses pointing to the control unit.
Fit the pre-assembled control unit on the transmission housing.
Tighten the M8 cylindrical screws to a torque of: 25 Nm.
Reconnect the electrical connector. Unscrew the plug marked PU. Connect the filling station. Using the external filling station it is possible to avoid dry operation of the hydrostatic pump and hydrostatic motor. Be sure to comply with the oil quantity and type. During the filling process, swivel the hydrostatic pumps and motors. Ensure the hydraulic unions are completely sealed. Fill the transmission oil with a filling station. Smear the mating face of the transmission housing with sealing product. Fit the cover.
Tighten the M12 screws to a torque of: 86 Nm.
Fit the pipe support. Refit the cab. Reassemble all hydraulic unions as marked at disassembly. Refit the spool valve support. Reconnect all electrical connections as marked at disassembly. Connect the heating pipes. Connect the air conditioning pipes. Check the levels of the various liquids.

Dyna VT - Disassembling and reassembling the pumps


The steering pump is fitted at the end of the variable displacement pump. It is a 19cc fixed displacement pump, with a 120 bar maximum pressure and a gear ratio of 67/58. It is fitted to the variable displacement pump by two CHC M8 screws. It rotates around a coupling sleeve. The variable displacement pump has maximum capacity of 60cc, and a 400 bar maximum pressure.
The gear ratio is 67/58. Drive is transmitted directly to the gearbox by a gear train. The pump is fitted to the gearbox housing by two HM 12 screws.
The lubricating pump is a fixed displacement pump. It is a gear pump and is fitted to the same drive pinion as the service pump. It’s capacity is 23.4cc.


Diagram of the variable displacement pump and steering pump 



Disassembling the steering pump and the variable displacement pump

Exploded view of the variable displacement pump 

Part list 
1 - O’ring, 2 – Flange, 3 – Screw, 4 – Hose, 5 – Gasket, 6 – Plug, 7 - O’ring, 8 – Washer, 9 - Rigid pipe,10 – Screw, 11 - O’ring, 12 – Union, 13 - Rigid pipe, 14 - O’ring,15 – Union,16 - O’ring,17 - Elbow union,
18 – Hose,19 – Screw, 20 – Flange, 21 - O’ring, 22 – Collar, 23 – Hose, 24 - O’ring, 25 – Screw, 26 - Washer

Exploded view of the steering pump 

Part list 
27 – Screw, 28 - Union plate, 29 – Hose, 30 – Union, 31 – Screw, 32 - O’ring, 33 – Hose, 34 – Union, 35 - O’ring, 36 - O’ring, 37 – Union, 38 – Strainer,39 – Seal,40 – Union,41 – Seal,42 – Union, 43 - Rigid pipe, 44 – Union, 45 - O’ring, 46 – Washer, 47 – Screw, 48 - O’ring, 49 – Union, 50 – Hose


Chock the tractor and take off the rear right-hand wheel. Remove the exhaust system. Take off the right-hand protective guards. Take off the protective guard over the right-hand footstep. Remove the right-hand footstep.
Drain and remove the fuel tank. Drain the hydraulic oil. Remove the protective housings that might obstruct access. Disconnect the hydraulic pipes connected to the tank. Disconnect the hose (33) from the steering pump priority block.
Take out the attachment screws (10) from the hydraulic pressure pipe of the variable displacement pump. Take out the tank attachment screws.
Remove the oil tank. Take out the rigid pipe (9) through the port, then disassemble it. Remove the hose (50) from the steering pump priority block.
Take out the attachment screws (27) from the union plate (28).
Gently remove the plate from the spacer, and disassemble the hydraulic union from the priority block. Remove the “Load Sensing” control pipe from the variable displacement pump. Disconnect the hose (33) from the steering pump priority block. Loosen the collar (22), then disconnect the variable displacement pump suction hose (23). Take off the rigid pipe (43) fitted with its strainer (38). Access to the union is limited, so a 41 mm pipe wrench is recommended. Remove the union (44) from the pump. Take out the attachment screws (47) from the steering pump. Remove the steering pump.
Discard the O’ring. Remove the coupling sleeve. Loosen and take out the screws (3), then remove the pressure union of the variable displacement
pump. Access is limited, so a 10 mm multipurpose wrench is recommended.
Remove the return rigid pipe (13) to the variable displacement pump tank. Access is limited, so a 27 mm pipe wrench is recommended. Remove the screws (25) from the variable displacement pump flange. Access is limited, so an 18 mm offset pipe socket is recommended. Support the variable displacement pump across the housing with a wooden shim, and pull the pump away of the gear teeth. Take the pump out of the spacer;
Discard the paper gasket. It is recommended to turn the suction channel of the pump upwards and to remove an attachment stud from the tank to extract the pump more easily.

Reassembling the steering pump and the variable displacement pump

Grease and fit new seals. Screw two M12 guide studs into M12 screw holes to assist pump assembly. Insert the variable displacement pump into the spacer and slide it onto the studs. A wooden shim can be fitted to assist pump positioning. Take out the guide studs and attach the pump using the two M12 attachment screws (25). Tighten the M12 screws (25) to a torque of: 86Nm
Fit the return rigid pipe (13) to the variable displacement pump tank. Access is limited, so a 27 mm pipe wrench is recommended. Fit the variable displacement pump pressure hose (4). Tighten the screws (3) to a torque of: 50Nm. Fit the coupling sleeve of the two pumps.
Fit a new O’ring on the steering pump centring diameter, and fit the steering pump in its housing. Fit and tighten the steering pump screws (47) to a torque of: 25Nm. Fit the steering pump union (44). Fit the steering pump rigid pipe (43) fitted with its strainer (38). Connect the hose (23) on the variable displacement pump suction channel, and tighten the collar (22). Attach the hose (33) on the steering pump priority block. Fit the elbow (17) on the variable displacement pump. Fit the steering pump priority block hose (50) and tighten the three screws (27) to a torque of: 10Nm.
Fit the hose (50) on the steering pump priority block. Take out the pressure hose (4) from the variable displacement pump through the spacer plug (6), and connect it to the rigid pipe (9) of the washer (8). Refit the stud if removed when extractng the pump. Clean the mating faces of the tank and spacer. Smear one of the cleaned surfaces with sealing product (ref. X903.050.074). Fit the hydraulic tank. Fit and tighten the tank attachment screws. Tighten the screws (10) of the washer (8). Fit the hose to the union (30). Fit the tank hydraulic channels. Refit the protective housings that were removed. Refit the fuel tank. Refit the footstep. Refit the protective guard over the right-hand footstep. Refit the right-hand protective guards.
Refit the exhaust system. Top up the hydraulic oil (approximately 65L). Check the operation and tightness of the hydraulic circuit. Repair any defective elements or seals. Refit the rear right-hand wheel.

Exploded view of the service pump (18 bar)

51 – Screw, 52 - Rigid pipe, 53 – Union, 54 – Screw, 55 – Union, 56 - O’ring, 57 - O’ring, 58 – Screw, 59 - O’ring, 60 – Cover, 61 – Catchdog, 62 - O’ring, 63 - Hydraulic pump, 64 - O’ring, 65 – Insert, 66 – Screw, 67 – Screw


Disassembling the lubricating pump

Exploded view of the lubricating pump 

Part list 
68 – Key, 69 – Washer, 70 – Screw, 71 – Screw, 72 - O’ring, 73 - O’ring, 74 – Filter, 75 – Screw, 76 – Cover, 77 - Suction filter, 78 - O’ring, 79 – Circlip, 80 – Pipe, 81 - O’ring, 82 – Pump, 83 - Drive pinion, 84 – Circlip


Remove the transmission unit. Take out the screws (75), then remove the cover (76). Remove the filter (74). Loosen the pipe on the pressure filter side.
Loosen the pipe on the rear axle side. Remove the circlip (79) from the suction pipe. Fit home the suction pipe in the suction filter pipe to release it from the pump. Loosen and remove the 2 screws (71). Remove the lubricating pump.
Remove the suction pipe. Discard the O’rings. Take off the pump pinion circlip (84). Remove the pump pinion (83). Take off the key (68).
Check the pump condition, and replace it if required.

Reassembling the lubricating pump

Fit the key (68) in its housing. Fit the drive pinion (83). Fit the shaft circlip (84). Fit the pump in its housing in the gearbox. Hold it in position using 2 screws. Refit the pipe on the pressure filter side and rear axle side.
Prepare the suction pipe. Fit the 2 O’rings (81) and circlips (79). Fit the side not fitted with the O’ring in the suction filter pipe (77). Smear the O'ring with miscible grease and fit home the pipe in the suction pump. The circlip groove on the suction filter pipe side must be cleared. Smear it with miscible grease, then slide the O’ring into its groove. Fit the circlip in its groove. Fit the pipe into the suction filter until it abuts against the circlip. Fit the circlip on the pipe, on the pump side. Definitively tighten the pump attachment screws to a torque of: 25 Nm. Fit the suction filter (74). Fit the cover (76) using the 3 screws (75). Tighten the screws (75) to a torque of:25Nm.  Refit the transmission unit.

Crankshaft - Remove and install


Removal Procedure

Remove the engine oil pump. Remove the front housing. Remove the crankshaft rear seal. Remove the rocker shaft and pushrods. If necessary, remove the cylinder head. If necessary, remove the pistons and connecting rods. The engine should be mounted on a suitable stand and placed in the inverted position. If the cylinder head, the pistons and the connecting rods have not been removed already, remove the connecting rod bearings.
Ensure that the main bearing caps are marked for the location and orientation.


Remove the setscrews (1) and the main bearing caps (2) from the cylinder block.


Remove the lower main bearing shells (3) from the main bearing caps (2). Keep the lower main bearing shells with the respective main bearing caps. The lower main bearing shells are plain bearings that have no oil holes.


Attach lifting straps and a suitable lifting device to the crankshaft (4). Lift the crankshaft (4) out of the cylinder block. The weight of the crankshaft is approximately 61 kg (134.5 lb). Do not damage any of the finished surfaces on the crankshaft. When the crankshaft is removed from the engine, the crankshaft must be supported on a suitable stand in order to prevent damage to the crankshaft timing ring.


Remove the upper main bearing shells (5) from the cylinder block. Keep the upper main bearing shells with the respective main bearing caps. The upper main bearing shells have a groove and two oil holes.
Remove the two thrust washers from number six main bearing in the cylinder block. If necessary, remove the crankshaft timing ring. If necessary, remove the crankshaft gear.

Installation Procedure

Clean the crankshaft and inspect the crankshaft for wear or damage. If necessary, replace the crankshaft or recondition the crankshaft. If necessary, install the crankshaft gear. If necessary, install a new crankshaft timing ring
Ensure that the parent bores for the bearing shells in the cylinder block are clean. Ensure that the threads for the main bearing setscrews in the cylinder block are clean and free from damage.
Clean the main bearing shells and the thrust washers. Inspect the main bearing shells and the thrust washers for wear or damage. If necessary, replace the main bearing shells and the thrust washers. If the main bearing shells are replaced, check whether oversize main bearing shells were previously installed. If the thrust washers are replaced, check whether oversize thrust washers were previously installed.
Install upper main bearing shells (5) to the cylinder block. Ensure that the locating tabs for the upper main bearing shells are seated in the slots in the cylinder block. The upper main bearing shells have a groove and two oil holes.
Lubricate the upper main bearing shells (5) with clean engine oil.
Attach lifting straps and a suitable lifting device to the crankshaft (4). Lift the crankshaft (4) into the cylinder block. The weight of the crankshaft is approximately 61 kg (134.5 lb). Do not damage any of the finished surfaces on the crankshaft. Do not damage the main bearing shells.


Lubricate the thrust washers (6) with clean engine oil. Install the thrust washers (6) into number six main bearing in the cylinder block. The thrust washers have a locating tab at one end. Ensure that the locating tabs are correctly seated in the cylinder block.
Install lower main bearing shells (3) into the main bearing caps (2). Ensure that the locating tabs for the lower main bearing shells are correctly seated into the slots in the bearing caps. The lower main bearing shells are plain bearings that do not have oil holes.
Lubricate the lower main bearing shells (3) and lubricate the journals of the crankshaft (4) with clean engine oil. Install the main bearing caps (2) to the cylinder block. Ensure the correct location and orientation of the main bearing caps (2). The locating tabs for the upper and the lower main bearing shells should be on the same side of the engine.


Lubricate the threads of the setscrews (1) with clean engine oil. Lubricate the underside of the heads of the setscrews (1) with clean engine oil.
Install the setscrews (1) to the main bearing caps (2). Evenly tighten the setscrews in order to pull the caps into position. Ensure that the caps are correctly seated. Do not tap the main bearing caps into position as the bearing shells may be dislodged.
Tighten the setscrews (1) to a torque of 80 N·m (59 lb ft). Turn the setscrews (1) through an additional 90 degrees. Use Tooling to achieve the final torque.
Rotate the crankshaft in order to ensure that there is no binding.
Check the crankshaft end play. Push the crankshaft toward the front of the engine. Install Tooling to the cylinder block and the rear face of the crankshaft. Push the crankshaft toward the rear of the engine. Use Tooling to measure the crankshaft end play. The permissible crankshaft end play is 0.17 mm (0.007 inch) to 0.41 mm (0.016 inch). If the crankshaft has been replaced or the crankshaft has been reconditioned, inspect the height of the piston above the cylinder block. If the crankshaft has not been replaced or the crankshaft has not been reconditioned, install the connecting rod bearings.
If necessary, install the pistons and connecting rods. If necessary, install the cylinder head.
Install the rockershaft and pushrods. Install the crankshaft rear seal. Install the front housing. Install the engine oil pump. 

Universal joint shaft brake


On some model tractors, the universal joint shaft brake comprises 6 discs and 6 intermediate plates, distributed on either side of a mechanism and activated by a control piston and a pin. The control piston is located on the right-hand side of the gearbox. The brake piston pushes the control rod, which activates
the brake plate. This then moves apart, and compresses the discs against the intermediate plates, which are splined together by pins (14). When released, the control plate springs ensure minimum clearance between the brake discs. Lubrication is ensured by an external hydraulic pipe coming from the lubricating circuit.


Exploded view of the universal joint shaft brake 
1 Shaft
3 Flange
4 Dowel pin
5 Allen screw
7 Brake plate
8 Ball
9 Spring
10 Dowel pin
12 Intermediate plate
14 pin
16 Universal joint shaft brake control piston
17 Control rod
22 Seal
23 Cylindrical screw
25 Stud
26 Nut

Cross-section view of the universal joint shaft Brake 



Disassembling the universal joint shaft brake

The following operations must first be carried out: Drain the transmission oil (approx. 65 litres). Split the tractor between the clutch housing and transmission housing. Remove the universal joint shaft. For easier reading, the work is carried out on a scale model. References are relative to figure.
Remove the suction filter of the variable displacement pump, if it obstructs disassembly (depending on model). Take off the internal leak pipe and deflector. Remove the lubricating oil pipe. Remove the control piston of the universal joint shaft brake (16). Take off the sleeve.
Remove the screws from the flange (5). Push out the flange (3) with two M8 screws. When pushing out the flange, the drive shaft must not leave its seat.
Take off the flange (3), discs (11), intermediate plates (12) and brake plate (7).

Reassembling the universal joint shaft brake

Before reassembly, all components, mating faces and grooves must be clean. Any rust, mud or water must be removed. Fit the studs (4).


Starting with an intermediate plate (12), fit 3 intermediate plates (12) and three discs (11) alternately. The first intermediate plate is fitted in position A. Use new intermediate plates (12) and new discs (11). Oil the discs before assembly.


The second intermediate plate is fitted in position B, and so on alternately.
Fit the brake plate (7). The control pin must be opposite the drilled hole.
Fit the control piston of the brake (16) with a new seal (22). Assemble the activating corner correctly as shown on the brake plate (7). Fit the remaining discs (11) and intermediate plates (12). Clean the mating face of the cover and smear with sealing product (ref. X 903.050.074).
Fit the flange (3) and tighten the screws (5) to a torque of: 50Nm
Check the axial clearance of the universal joint shaft with a dial gauge.

Specified value: 0.3 + 0.1mm
If outside the specified value, correct the clearance with compensating shims.
Fit the lubricating pipe, return pipe and deflector. Fit a new suction filter.
Grease and install a new O’ring. Insert the sleeve on the shaft (1).

Adjusting the brake control piston:
Unscrew the locknut. Tighten the adjustment rod with a torque wrench (or the corresponding torque gauge, ref. X 899.980.151); to a torque of: 4 to 5Nm
Unscrew the rod by 3.6 turns and lock it in this position. Assemble the tractor between the clutch housing and transmission housing. Refit the universal joint shaft. Fill up the transmission oil.

Disassembling the universal joint shaft brake control

Remove the hydraulic pipe. Loosen and remove the brake cylinder attachment screws. Remove the brake cylinder and control rod. Discard the paper gasket.

Reassembling the universal joint shaft brake control

Clean the mating faces of the gearbox and brake cylinder. Smear the control lever ball joint with miscible grease. Fit the control rod in the brake cylinder.
Oil and fit a new paper gasket. Fit the control rod / brake cylinder assembly in the gearbox housing. Fit and tighten the brake cylinder attachment screws.
Reconnect the hydraulic pipe. Bleed the brake.

Main braking circuit of Dyna VT transmission




Tractors with a DYNA VT transmission are fitted with a hydraulic braking system operating on the high pressure auxiliary circuit for the rear brakes and on the transmission low pressure circuit for the front axle shaft brake. They are both controlled by a braking valve activated by two pedals that can operate coupled or uncoupled. The braking valve, located at the front of the pedal, receives and directs pressure to the various components. It controls:
- The right- and left-hand brakes located under the rear axle, and operating simultaneously or separately,
- the front axle shaft brake control,
- the trailer brake control via a pressure sensor located on the valve.

Rear brakes
Located in the rear axle, the two disc brakes are independent. Each brake is controlled hydraulically by a cylinder, or mechanically by the ParkLock ram. The braking valve is supplied by the make and break valve located under the distribution block with an accumulator that maintains a pressure reserve of 135 – 165 bar. The braking valve includes a pressure relief valve (0-70 bar). The pressure is distributed to the brake by two spools located on either side of the pressure relief valve.

Front axle shaft brake
The front axle brake is located at the front of the gearbox. It is a hydraulically controlled multidisc brake.
The main braking valve controls a power-assisted braking valve which operates the front brake under a 18 bar max. pressure (transmission low pressure circuit).

Trailer brake
The trailer brake is controlled electro-hydraulically. A pressure sensor informs the Autotronic 5 calculator of the pressure in the braking circuit. This then activates a proportional solenoid valve that controls the trailer brake valve via the transmission 18 bar circuit.




Characteristics of braking components

Braking valve
- Braking pressure: 0 to 70 bar.
- Working travel: 16 mm
Rear brakes
- Piston diameter: 50.8 mm
- Piston stroke: 3.7 mm
- Maximum volume used by piston: 12.25 cm3 on each side
Front brakes
- Piston diameter: 62 mm
- Piston stroke: 6.1 mm
- Rear brake / front brake pressure ratio: 2.04 bar
- Maximum braking pressure: 18 bar

Braking valve control


Parts list 
(1) Main braking valve block (2) Braking pressure regulator (3) Left-hand brake control (4) Right-hand brake control (5) Pedals (6) Bearing (7) Bearing (8) Bearing (9) Bearing (10) Sensor (11) Spring


Identification of ports 
(P) High pressure supply
(T) Tank return
(X) Control of front axle shaft brake and trailer brake pressure sensor
(F1) Left-hand brake supply
(F2) Right-hand brake supply

Braking control
The pedals are pressed against the braking valve rods via bearings (6) (7) (8) (9). Each pedal simultaneously controls the pressure regulator and corresponding spool valve (3) or (4).

Relations between the different tractor braking circuits

The braking circuits of the rear axle, front axle and trailer are hydraulically or electrically linked. These circuits must react simultaneously to a single action on the brake pedals.


Parts list 
(P1) High pressure variable displacement pump
(P2) Transmission low pressure hydraulic pump
(PB) Trailer brake and ParkLock priority valve
(CD) Make and break valve
(TV) Trailer braking valve
(BV) Tractor braking valve
(EV) Trailer brake control proportional solenoid valve
(AC1) Accumulator (ParkLock)
(AC2) Accumulator (rear brakes)
(TB) Trailer brake
(BR1) Rear brake
(BR2) Rear brake
(BP1) Pedal
(BP2) Pedal
(M) Pressure sensor
(FD) Front brake control valve
(BF) Front brake
(AUX) To non-priority components
(AUTO 5) Autotronic 5 calculator
(PARKLOCK) ParkLock assembly (ram and control)

Action on tractor brakes

Pedals coupled
When one of the two pedals (BP1) and (BP2) is activated, the pressure regulator located in the braking valve regulates the pressure coming from the make and break valve (CD) and accumulator (AC2). The braking valve then distributes this pressure to the rear brakes (BR1) and (BR2).
Simultaneaously, the braking valve sends a pressure signal to the spool valve (FD) and pressure sensor (M). The spool valve (FD) controls the front axle brake (BF) with pressure from the pump (P2) (transmission 18 bar circuit). The sensor (M) allows the Autotronic 5 to control the trailer brake via the proportional solenoid valve (EV).

Pedals uncoupled
If the driver presses on just one pedal, this acts on the braking valve pressure regulator and on a brake spool valve. The pressure is directed to the corresponding brake. The “&” valve in the braking block ensures no pressure signal is supplied to the spool valve (FD) or sensor (M). The front brake (BF) and trailer brake (TB) are only activated when both brake pedals are simultaneously activated.

“&” Valve
The “&” valve is fitted in the braking block. It allows pressure to be supplied to the trailer brake and front brake only if the two pedals are activated. The pressure directed to the rear left- and right-hand brakes must be identical to enable operation of the front brake and trailer brake.

Diagram


Parts list 
(1) Tractor braking valve
(2) Pressure relief spool
(3) Right-hand brake spool
(4) Left-hand brake spool
(5) Right-hand brake
(6) Left-hand brake
(7) & Valve
(8) Accumulator (braking circuit)
(9) Accumulator (ParkLock circuit)
(10) Transmission low pressure circuit pump
(11) Front axle shaft brake control spool
(12) Front axle shaft brake
(M1) Braking circuit load pressure switch
(M2) Braking circuit load pressure switch
(TR 34) Trailer braking pressure sensor
(A) Trailer brake control
(B) To ParkLock
(C) Braking circuit supply pressure from make and
break valve (135 - 165 bar)

Rear brake cylinders

The rear brake cylinders are located on the rear axle, beside the trumpet housings.

Description 
The rear axle braking system consists of a brake cylinder (1), a piston (2), and a rod (5) that acts on an assembly (3) comprised of discs (6) and intermediate plates (7) (see chapter 6). The brake disc assembly is fitted before the final drive unit (4) in the rear trumpet housing. The piston acts on the rod (5) whose triangular end allows the two intermediate plates (9) and (10) to swivel in relation to each other. When swivelling, the intermediate plates (9) and (10) are kept separate by balls (8). Return springs (18) restore the intermediate plates (9) and (10) to position when the brakes are released. The port (16) is linked to the bleed circuit by a pipe.


Operation
Braking can be activated hydraulically (brake pedals) or mechanically (ParkLock).

Pedal braking
The braking pressure (coming from the braking valve) arrives at the cylinder via the port (14). The piston (2) is forced down by the pressure, driving down the lower part of the piston (17) and rod (5) and activates the braking mechanism.


Mechanical braking (ParkLock)
When the brakes are activated by the ParkLock ram, the levers (18) activate the cams. As they rotate they drive the lower part of the pistons (17) and rod (5) and activate the braking mechanism. When the lower part of the piston (17) has lowered, the spring (15) keeps the upper part of the piston (2) at the top of the cylinder.

Removing the universal joint shaft brake 
The front axle shaft brake is located at the front of the gearbox.


Operation
The front axle shaft brake operates in a similar manner to the rear brakes. A piston pushes a rod (21) with a triangular end. The triangular part allows two intermediate plates to swivel in relation to each other, while they are held apart by balls (23).



Bleeding the brakes


The tractor brakes are bled through bleed plugs located at the rear right-hand side of the tractor beside the auxiliary spool valves:
(1) Front axle shaft brake
(2) Rear left-hand brake
(3) Rear right-hand brake
The trailer brake is bled through the bleed plug located on top of the distribution block. The brakes must be bled every 1200 hours, or when working on the braking circuit.

Bleeding method
Start the engine. Open the right-hand (3), left-hand (2) and front (1) bleed plugsPress moderately on the coupled brake pedals, with pedal travel of approximately 20 mm. Never press the pedals down more than 25 mm when the bleed plugs are open. A jet of oil under pressure will spurt out of the bleed plugs.


Let the air bleed out at the plugs.
Close the plugs again when the fluid coming out no longer shows any trace of foam or air bubbles. Release the pedals. Open the bleed plug on the trailer brake valveRepeat the operationsCheck the oil levels in the auxiliary hydraulics and gearbox.