Removing and install the differential unit assembly


Split the tractor between the intermediate housing and the centre housing.
If necessary, separate the PTO housing from the centre housing.
Remove the trumpet housings. Take off union (44) and raise the transfer tube (42). 


Unscrew the ground speed sensor to avoid interference with the crownwheel.
Remove the brake pistons.
Place and tighten sling ref. 3378116M1, in position corresponds to a differential assembly with a hydromechanical differential lock and a rear axle with a Full Powershift or Heavy gearbox. Using the sling, hold the differential assembly in the axis of the left and right-hand carriers (27) (38).

Removing the differential unit
Remove bolts (26) (39) from the differential lock carriers and fit the guide bolts "G". Extract and remove the differential lock carriers using the tapped holes and the two bolts "V". Recover the differential lock spring (47) installed in the left-hand differential lock carrier (38).


Remove the o’rings (34).
Take out the lock assembly and the differential (36) from the centre housing.
Since space is limited around the differential unit, it is vital to Install the auxiliary spool valve and lift control valve the oil return pipe in the housing (45) before refitting the unit.


Using the sling, introduce the differential assembly into the centre housing and hold it in the axis of the trumpets.
Reinstall the left and right-hand side differential lock carriers.
After fitting the differential lock carriers, manually check the rotation of the differential assembly. Reinstall the brake pistons.
- If the carrier (1) of the ground speed sensor (2) has been removed, position the carrier previously lightly smeared with Loctite 510 or its equivalent, with the offset of the sensor turned towards the longitudinal axis of the centre housing. Tighten the bolts (3) previously lightly smeared with Loctite 542 to a torque of 25 - 35 Nm.
- The end of the sensor must always be placed above the teeth of the differential crownwheel.
- Install and adjust the ground speed sensor lightly smeared with Loctite 577 (Sensor Sealing or equivalent).


Reinstall the trumpet housings.
If the PTO housing has been removed, assemble it with the centre housing.
Couple the tractor between the intermediate housing and the centre housing.
Check the correct operation of all the controls (mechanical, hydraulic and electronic). Carry out a road test. Check the oil tightness of the mating faces and hydraulic unions.

Removing and install the planetary gears and sun gears and disassembling and reassembling the crownwheel

Remove the differential unit.


Remove the fixed dog (46).
Separate the differential half-housings (23). These components both bear the same number. They must always be fitted as pairs.
Remove the sun gears (30), planetary gears (29), washers (28) and the differential brace (33).


If necessary, drive cup (32) off the differential halfhousing (23), recover the shim(s) (59). Extract and discard the deflector (20).

Disassembling the crownwheel
- The replacement of the crownwheel automatically requires replacement of the drive pinion.
- Both parts bear the same number.
- They must always be installed as pairs.
- The original factory parts are assembled using rivets
- During repairs, these rivets are replaced by nuts and bolts and are referenced in the spare parts catalogue.
Centre punch each rivet (24) (on toothed side of crownwheel). Using a 5 mm drill, drill out the rivets to a depth of 12 mm. Carry out a second drilling operation using a 12 mm drill to the same depth. Drive out the rivets using an appropriate drift.

Install the crownwheel
Clean the mating faces of the new crownwheel (22) and differential half-housing (23) as well as their nuts and bolts.
Lightly smear the first few threads of the bolts with Loctite 270 and place them in the crownwheel and housing.
Tighten the nuts to a torque of 150 - 200 Nm.

Install planetary gears and sun gears

Special points
- If replacement of the friction bushes (35) (61) is necessary, insert the new bushes lightly smeared with Loctite 638 or equivalent, using a suitable fixture.
- Check after insertion that the lubricating ports have not been blocked by Loctite.
- If necessary, insert deflector (20) and cup (32).
Reinstall the planetary gears and sun gears. Reinstall the fixed dog (46).
Lightly smear bolts (41) with Loctite 270 or its equivalent and tighten them to a torque of 130 Nm. Reinstall the differential assembly and the brake pistons.
Finish the refitting of the different assemblies.

Adjusting and checking the backlash

- The backlash between the crownwheel and drive pinion ensures reliability of the bevel gear and the correct operation of the assembly. This clearance must be checked after:
. adjusting the bevel gear distance
. shimming the differential unit.
- Using an appropriate extractor, remove cup (32) and discard the deflector (20).

Pre-adjustment
- The thickness of the shim(s) "E" required to obtain the correct backlash is calculated as follows: E = Dc + 0.10 mm
E: thickness of shim(s) (59) to be fitted
Dc: crownwheel offset
- The Dc (example shown: -0.40) engraved on the external diameter of the crownwheel after the pairing number and letter (39 K) may range between 0 and -0.60 mm.


Special point
- When calculating "E" do not take the negative sign preceding the Dc into consideration.
Place the previously selected shim(s) (59) in the bore of the half-housing (23). Insert the deflector (20) and cup (32).
- The deflector serves as a guide for centring the shims. It is inserted using the cup and an appropriate locally manufactured tool. This method allows the deflector to rest against the cup both during and after its insertion.
- When the operation is completed, check that the cup is thrusting on the shim(s) and in contact with the deflector.
Reinstall the right-hand differential lock carrier and shim the differential unit.

Checking
- Couple and provisionally fix the intermediate housing to the centre housing using several diametrically opposed bolts tightened to a torque of 540 - 680 Nm.
- With the PTO housing taken off, through the rear opening of the centre housing (45), place the index of a dial gauge half way across the length of a tooth of the crownwheel.
- Check that the backlash is between 0.15 mm and 0.45 mm. Carry out this check at three points around the crownwheel.
- If the backlash is incorrect, the adjustment principle is to reduce or increase the thickness of shim(s) (59).
- In this case, select and Install a different thickness of shim(s). Carry out the shimming of the differential unit again in order to obtain the pre-loading of bearings (31) (32) and (54) (57).
- Check a second time, the backlash between the drive pinion and the crownwheel.
- When the final adjustment has been obtained, go on with the installing operations.

Shimming the differential unit

If the centre housing (45), crownwheel, taper roller bearings and carriers (27) (28) have been replaced, the differential unit must be shimmed. Check beforehand that the shim(s) (59) used for the backlash are installed in the half-housing (23) and cup (32).

Shimming preparation
Place the differential assembly previously installed with bearing cone (54) in the housing using sling ref. 3378116M1. Screw two diametrically opposed guide studs into the centre housing.

Assembly of the right-hand differential lock carrier
- Insert the carrier (27) fitted with a new o’ring (34) using four bolts (26). Remove the guide studs. Finish Installing the four bolts and tighten to a torque of 100 - 130 Nm.
At the location of the left-hand side differential lock carrier, place tool ref. 3378117M1, adapted for the standard differential unit with hydromechanical differential lock. Using two bolts, fix the tool onto the housing.


Tighten the centre bolt to 10 Nm. Turn the crownwheel several times to seat the cones correctly in the cups. Check the tightening torque of the centre bolt again.

Dimension to be measured on the housing (45)


Using an appropriate depth gauge, measure dimension "B" and determine dimension "C" between bearing cup (57) and the seating face of the carrier (38) on the housing:
C = B - 10 mm (10 mm is the thickness of tool, ref. 3378117M1).


Dimension to be measured on differential lock carrier (38) 


Using appropriate tools (depth gauge, calliper, rule) so as order to carry out the measurement under the best conditions, measure dimension "Y".
Calculate distance "E" between the seating faces of bearing cup (57) and carrier (38): E = C – Y
Fill in space "E" with a deflector (shim) of a thickness shown in the following table, so as to obtain a P2 preloading of 0.05 mm to 0.15 mm.


Remove the tool and the bearing cup (57).
On differential lock carrier (38), check for the presence of centring bush (40) and place the deflector (55) (shim) determined in operation 74 and cup (57).
Insert the carrier. After Installing the differential lock carriers, manually check the rotation of the differential assembly.