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.