Hypoid bevel gear differential and multidisc lock - planetary gears, sun gears and crownwheel

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

Remove the differential unit assembly. Remove the locking system.

Removal

Remove the left-hand sun gear (33). To remove the half shafts (35), it is necessary to disassemble the crownwheel. Remove bolts (39).

Take out pins (38) from unit (21). Push on a half shaft in the direction of the arrow to drive out the opposite half shaft. Repeat the operation for the remaining half shafts. Recover the spherical washers (30). Remove the planetary gears (31). Remove the differential yoke and the right-hand sun gear (32). If necessary, drive cup (28) off the unit (21) and recover the shim(s) (29).

Disassembling the crownwheel

The replacement of the crownwheel automatically requires replacement of the drive pinion. Both parts bear the same number and they must always be fitted as pairs.

Remove bolts (22).

Refitting the crownwheel

- During repairs, use the bolts referenced in the spare parts catalogue.

Clean the mating faces of the new crownwheel (20) and unit (21) as well as bolts (22).

Screw two diametrically opposed guide studs into the tapped holes of the crownwheel. Assemble the crownwheel on the unit. Smear the first few threads of the bolts with Loctite 270 and screw them into the crownwheel. Remove the guide studs. Tighten and lock the nuts at a torque of 240 - 320 Nm.

Refitting planetary gears and sun gears

If necessary, place shim(s) (29) and insert cup (28) in unit (21).

- If replacement of the friction bushes (36) (37) is necessary, insert the new bushes lightly smeared with Loctite 638 using a suitable fixture.

- Check after insertion that the lubricating ports have not been blocked by Loctite.

Refit the right-hand sun gear (32) in the friction bush (36). Refit the differential yoke (34) as shown in the overall view. Check that the central channels and radial drilled passages in the half shafts (35) are not obstructed.

Assemble planetary gears (31), friction washers (30) and the half shafts, with the holes turned towards bolt (39) as shown in the overall view.

Position the shafts. Fit and tighten bolts (39) lightly smeared with Loctite 270 and tighten them to a torque of 25 - 35 Nm.

Manually check the rotation of the planetary gears and the right-hand sun gear (32). Refit the crownwheel. Refit the intermediate plates, discs and cover. Refit the differential unit assembly and the brake pistons. Fit and adjust the forward speed sensor. Refit the transfer tube (41) and union (44). Finish the refitting of the different assemblies.

Adjusting and checking the multidisc

The backlash between the crownwheel and drive pinion ensures reliability of the bevel gear and the correct operation of the assembly. This backlash must be checked after:

- adjusting the bevel gear distance

- shimming the differential unit.

Disassembly

Using an appropriate extractor, remove cup (28).

The thickness of the shim(s) "E" required to obtain the correct backlash is calculated as follows: E = Dc + 0.10 mm where:

E : thickness of shim(s) (29) to be fitted

Dc : crownwheel offset

- The Dc (example shown: -0.10) engraved on the external diameter of the crownwheel after the pairing number and letter (31 A) may range between 0 and -0.60 mm. When calculating �E� do not take the negative sign preceding the Dc into consideration. Place the previously selected shim(s) in the bore of the unit (21). Insert bearing cup (28) and check that it is in contact with the shims. Refit and shim the differential unit.

Checks

- Couple and temporarily 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 multidisc 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) (29).

- In this case, select and fit a different thickness of shim(s). Carry out the shimming of the differential unit again in order to obtain the pre-loading of bearings (27) (28) and (46) (47).

- Check a second time the backlash between the drive pinion and the crownwheel.

When the final adjustment has been obtained, go on with the refitting operations.

Shimming the differential unit

If the centre housing (45), crownwheel, taper roller bearings and carriers (25) (40) have been replaced, carry out shimming of the differential unit. Check beforehand that the shim(s) (29) used for providing the multidisc are fitted between unit (21) and cup (28).

Shimming preparation

Place the differential assembly in the housing using sling ref. 3378116M1. Screw two diametrically opposed guide studs into the centre housing. Insert carrier (25) fitted with a new O�ring (26) using four bolts (24). Remove the guide studs. Complete the refitting of the other bolts and tighten to a torque of 100 - 130 Nm. Remove bearing cone (46) and shim(s) (48) from carrier (40).

Slide bearing cone (46) on tool, ref. 3378117M1, adapted for the hypoid differential unit with multidisc 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" at two opposed points (work out average of the two measurements) and determine dimension "C" between bearing cup (46) and the thrust face of the carrier (40) on the housing: C = B � 10 mm(10 mm is the thickness of tool, ref. 3378117M1). Dimension to be measured on carrier (40).

Measure dimension "Y" using an appropriate depth gauge and rule.

Calculate distance "E" between the thrust faces of bearing cup (46) and carrier (40): E = C � Y. Fill in space "E" with a thickness of shims (48).

In space "E", add additional shims between 0.05 mm and 0.15 mm, in order to obtain P2: P2 = 0.05 mm to 0.15 mm. Remove the tool and bearing cup (46).

Hypoid bevel gear differential and multidisc lock - Remove and refit the differential and multidisc lock

Removing and refitting the differential unit assembly

Preparation for fitting

Uncouple 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 2 (this position corresponds to a differential assembly with a multidisc differential lock on the rear axle with an AG250 Full Powershift gearbox). Using the sling, hold the differential assembly in the axis of the left and right-hand carriers (25) (40).

Removing the differential unit

Remove bolts (24) from the carriers and fit the guide bolts "G" in accordance with Figure. Extract and remove the carriers by inserting two bolts "V" through the tapped holes as shown in Figure. Recover the cone (46) and shims (48) from carrier (40). Remove the O�rings (26).

Take out the differential assembly from the centre housing.

Refitting

Since space is limited around the differential unit, it is essential to fit the auxiliary spool valve and lift control valve return pipe in the housing (45) before refitting the unit. In order not to damage the seal rings (49), it is necessary to correctly align the differential assembly along the axis of the centre housing before inserting carriers (25) (40).

Using the sling, introduce the differential assembly into the centre housing and hold it in the axis of the trumpet housings.

Assembling the right-hand carrier (25)

Screw two diametrically opposed guide studs into the centre housing. Check for the presence of centring bush (23). Lubricate and fit a new O�ring (26). Insert the carrier (25) using the four bolts (24) uniformly and alternately tightened to a torque of 100 � 130 Nm. Tighten the other bolts to the same torque.

Assembling the left-hand carrier (40)

Slide bearing cone (46) on to tool, ref. 3378117M1, adapted for the differential with hypoid bevel gear and multidisc lock. Using the tool, centre the differential assembly in the housing by manually turning the central bolt clockwise until it encounters resistance. Screw two diametrically opposed guide studs into two holes in the centre housing, their ends thrusting

against cover (50) of the differential lock. This method allows the centring of the differential assembly to be retained after removal of tool ref. 3378117M1, in order to later provide a correct fitting of the left-hand carrier (40) without damaging the seal rings (49). Remove the tool and recover the bearing cone (46). Check for the presence of centring bush (23) in the housing and fit a new O�ring (26) on to carrier (40).

Check that the seal rings (49) have not been damaged and that they turn normally in their grooves. After this check, remove the seal rings (and coat them with miscible grease so that they remain at the bottom of the groove during refitting of the carrier. Place shim(s) (48) and slide the bearing cone (46) on carrier (40). Insert the carrier into the housing using the four bolts (24) uniformly and alternately tightened to a torque of 100 - 130 Nm. Tighten the other bolts to the same torque. After fitting the carriers, manually check the rotation of the differential assembly. Refit the brake pistons.

Special points

- If the carrier (1) of the ground speed sensor (2) has been removed, position the carrier previously lightly smeared with Loctite 510, with the offset of the sensor turned towards the longitudinal axis of the centre housing as shown in Figure.

- 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 crownwheel of the differential.

- Fit and adjust the ground speed sensor lightly smeared with Loctite 577 (Sensor Sealing or equivalent).

Refit transfer tube (41) and union (44). Refit 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 controls (mechanical, hydraulic and electronic). Carry out a road test. Check the oil tightness of the mating faces and hydraulic unions.

Removing and refitting the multidisc lock

Remove the differential unit.

Removal 

Place the differential unit with the lock turned upwards. Loosen and take out bolts (51). Take off the cover (50). Separate the discs (56) and intermediate plates (55) from the left-hand sun gear (33). Gently tap the cover (50) on a wooden block to remove the piston (52). Remove O�rings (53) (54).

If necessary, drive out cup (47).

On the left-hand carrier (40)

Remove the seal rings (49) and O�ring (42).

Reassembly

If unit (21), cover (50) and carrier (40) have been replaced, it is mandatory to carry out shimming of the differential unit and to check the backlash between the drive pinion and the crownwheel.

Clean and check the components. Replace any parts found to be defective.

Check that the hydraulic channel in cover (50) is not obstructed. Lubricate and fit new O�rings (53) (54) on piston (52). Insert the piston by tapping around its rim with a plastic hammer. Check that there are no seal fragments after insertion. Assemble the intermediate plates (55) and discs (56) as shown in the overall view.

Position cover (50) fitted with piston (52). Fit bolts (51) lightly smeared with Loctite 270 and tighten to a torque of 100 - 130 Nm. Manually check that the discs and intermediate plates are not constrained in any way.

Differential with hypoid bevel gear and multidisc lock

The tractors is equipped with an AG250 Full Powershift gearbox and have a wide intermediate housing in which the axial position of the drive pinion has been redesigned for the fitting of a hypoid bevel gear.

Parts list

(1) Bearing cone (2) Bearing cup (3) Shim(s) (4) Thrust washer (5) Circlip (6) Intermediate plates (handbrake) (7) Bearing cone (8) Bolt (9) Drive pinion (10) Bearing cup (11) Bolt (12) Shim(s) (13) Bearing carrier (14) Discs (15) Handbrake unit (16) Mechanism (17) 4 WD drive pinion (18) Nut

(19) Intermediate housing (20) Crownwheel (21) Unit (22) Bolts (23) Centring bushes (24) Bolts (25) Right-hand carrier (26) O�rings (27) Bearing cone (28) Bearing cup (29) Shim(s) (30) Spherical washer (31) Planetary gear (32) Right sun gear (33) Left sun gear (34) Differential yoke (35) Planetary gear half shafts (36) Shouldered bush (37) Shouldered bush (38) Needle bearings (39) Bolt (40) Left-hand carrier (41) Transfer tube (42) O�ring (43) O�ring (44) Union (45) Centre housing (46) Bearing cone (47) Bearing cup (48) Shim(s) (49) Seal rings (50) Cover (51) Bolt (52) Piston (53) O�ring (54) O�ring (55) Intermediate plates (differential lock) (56) Discs (57) Lubricating pipe (58) Rivet (59) Rivet

Construction

The bevel gear, moved in rotation by the gearbox output shaft, drives the rear axle. The helical drive pinion is supported by two taper roller bearings mounted in opposition. The bearing cone (7) is force fitted on the drive pinion, and cups (2) (10) are likewise force fitted into the intermediate housing (19) and bearing support (13). The bearing cone (1), mounted free on the drive pinion, allows to fit the shims (3) required for shimming. The crownwheel is fastened to the differential housing by bolts. The differential assembly rotates on two taper roller bearings supported by two lateral carriers centred by bushes (23) and fixed by bolts to the housing. The differential assembly is formed by two halves holding four planetary gears (31) and two sun gears (32) (33). The left-hand side sun gear also serves as the hub for the differential lock discs (56). The planetary gears turn on four half shafts (35) housed in the unit and the differential yoke (34). They are held in place by pins and bolts. 

The lubrication of the planetary gears is carried out by axial and radial channels drilled in the half shafts. The sun gears, left-hand carrier (40), cover (50) and the differential yoke contain drilled lubrication channels allowing

transmission oil to reach bushes (36) (37), discs (56) and the differential lock system. The drive pinion, which bears the 4 WD drive pinion (17), is located in the intermediate housing. The adjustment of its position is carried out by shims (12) fitted between the bearing carrier (13) and the housing. The pre-loading of the bearings is obtained by shim(s) (3) fitted between the bearing cone (1) and the thrust washer (4). The preloading via shimming of the differential assembly is carried out via shim(s) (48) placed between bearing cone (46) and the left-hand carrier (40). Backlash of the drive pinion and the crownwheel is obtained by using shims (29) inserted between cup (28) and the differential half-housing (21).

Differential lock

The multidisc lock system comprises:

- a unit (21) housing the discs (56) and intermediate plates (55).

- a hub (33) integral via splines with the left-hand trumpet input sun gear.

- a cover (50) made up by piston assembly (52) and supported by taper roller bearings (46) (47).

The piston chamber lodged in the cover communicates with a channel in the left-hand carrier (40), allowing (17 bar) low pressure to act upon the piston. Two seal rings (49) ensure the oil tightness of the circuit.

Operation

Clutched position

When the differential lock solenoid valve is activated, the pressure flows through the channels in left-hand carrier (40) and cover (50) on unit (21) and enters piston chamber (52). The piston compresses the intermediate plates (55) and discs (56) integral respectively via stops and splines in lock unit (21) and hub (33). In this �clutched� position, the input sun gears of the righthand and left-hand trumpets turn at the same speeds.

Declutched position

When the pressure is cut, the piston returns, the discs and intermediate plates are no longer compressed and allow the sun gears and planetary gears to carry out their differential function.

Removing and refitting the carriers

Left-hand carrier

It is possible to carry out maintenance on carrier (40) and seal rings (49) of the differential lock by removing only the left-hand trumpet housing.

Removal

Remove the left-hand trumpet housing.

Take off union (44) and raise the transfer tube (41). Remove the brake piston.

Remove bolts (24) on from the left-hand carrier. Place two diametrically opposed guide studs "G" on the housing as shown in Figure, their ends pushing against cover (50) of the lock unit.

Extract the carrier by inserting two bolts "V" through the tapped holes; take it off and recover cone (46) and shim(s) (48). The guide studs "G" hold and centre the differential assembly in the housing. Do not unscrew the guide studs. This may throw off centre the assembly and damage the seal rings (49) during refitting of the carrier.

Refitting

Check for the presence of centring bush (23) on the housing, the shim(s) (48) and bearing cone (46). Check that the seal rings (49) are not damaged and that they turn normally in their grooves. After this check, remove the seal rings and coat them with miscible grease, so that they remain at the bottom of the groove during refitting of the carrier. Fit new O�rings (26) (42).

Slide the carrier onto the guide studs"G" and alternately and uniformly tighten the four bolts (24) to a torque of 100 - 130 Nm. Remove the guide studs. Fit and tighten the other bolts to the same torque. Position the transfer tube (41) in carrier (40). Screw in and position union (44). Refit the brake piston.

Check the oil tightness of seal (26) on carrier (40). Refit the left-hand trumpet housing.

Right-hand carrier

The access to the right-hand carrier (25) is similar to that of the left-hand carrier (40).

Removal

- Take out bolts (24) and place diametrically opposed guide studs "G" in the housing, their ends thrust against the half-housing (21).

- Extract the carrier by inserting two bolts "V" through the tapped holes and remove it.

Refitting

- Check for the presence of the centring pin (23) on the housing and O�ring (26).

- Tighten uniformly and alternately the four bolts (24) to a torque of 100 - 130 Nm. Remove the guide studs. Fit and tighten the other bolts to the same torque.

- Check the oil tightness of seal (26) on carrier (25).

Standard bevel gear differential and multidisc lock - Remove and refit the drive pinion

Uncouple the tractor between the intermediate housing and the centre housing. Remove the creeper unit (if fitted). Free the ratchet of the Park Lock transmission lock (if fitted). Locate the position of and take out the sleeve linking the drive pinion and the lower shaft. Remove the hydraulic pump bearing / drive pinion assembly.

Removing the drive pinion

Disconnect control pin (25) of the handbrake mechanism.

Release and immobilise nut (18) using wrench, ref. 3378118M1. Place special socket ref. 3378119M1, on the end of the drive pinion and turn it clockwise.

Remove bearing cone (1), shims (3) and thrust washer (4).

Take out two diametrically opposed bolts (11) on bearing carrier (13). In their place screw two guide studs "G" into the tapped holes. Remove the other bolts.

Extract carrier (13) using two bolts "V" of sufficient length placed in the tapped holes. Take off the carrier (13) assembly / unit (15), shims (12) and 4 WD pinion (17) (if fitted). Visually note the position of the components.

Remove circlip (5). Unscrew and remove bolts (8). Separate the carrier (13) and the unit (15). Remove the discs (14), the intermediate plates (6) and the handbrake mechanism (16). If necessary, extract the bearing cups (2) (10) and cone (7) from the drive pinion.

Refitting the drive pinion

If the drive pinion, the taper roller bearings (7) (10) (1) (2), bearing carrier (13), thrust washer (4) and intermediate housing (19) have been replaced, it is essential to adjust the position of the drive pinion (bevel distance) and then shim the taper roller bearings).

Clean and check the components. Replace any parts found to be defective.

If bearing cone (7) has been disassembled, insert it to thrust against the drive pinion and cup (10) in contact with bearing carrier (13), using a press and an appropriate fixture. Lubricate the taper roller bearings (7) (10) with transmission oil. Refit mechanism (16), the intermediate plates (6) and discs (14). Assemble unit (15) and carrier (13).

Screw two diametrically opposed guide studs into the tapped bolt holes (11).

Position and slide shims (12) on to the guide studs.

Check that the 4 WD drive pinion (17) (if fitted) is oriented as shown in the overall view. Correctly position the carrier assembly (13) and unit (15) on the guide studs. Turn the drive pinion so as to engage the splines in pinion (17). Continue to push the unit assembly until it reaches its inserted position.

Use the remaining bolts (11) and insert uniformly and alternately the carrier assembly (13) and unit (15). Remove the guide studs. Lightly smear bolts (11) with Loctite 270 and tighten them to a torque of 100 - 130 Nm.

Check that carrier (13) is in contact with shims (12). It is essential to place thrust washer (4) against shoulder "E" of the drive pinion. Slide on shims (3). Lubricate the bearing cone (1) with transmission oil and fit it on to the drive pinion in contact with the shims. Degrease the threads of nut (18) as well as those on the drive pinion. Lightly smear the threads of the nut with Loctite 270 or its equivalent and immobilise it using wrench, ref. 3378118M1. Using socket, ref. 3378119M1, turn the drive pinion anti clockwise and tighten it to a torque of 200 - 250 Nm.

Take care to correctly position the torque wrench. Remove the tool. Manually check the rotation of the drive pinion. Lock the nut by bending the lock washer into the grooves of the pinion without breaking it, using an appropriate tool.

Fit pin (25) into the handbrake mechanism, correctly positioned to provide clearance. Place the washer and retaining pin. Adjust the control.

Final operations

Refit the hydraulic pump bearing / drive pinion assembly.

Refit the ratchet and locking sleeve of the Park Lock transmission (if fitted). Refit the creeper unit (if fitted). Adjust the fork.

Re-couple the tractor between the intermediate housing and the centre housing. If the crownwheel and drive pinion have been replaced, check the backlash. Check the operation of all the controls. Carry out a road test.

Check the oil tightness of the mating surfaces. Check the oil tightness of the hydraulic unions.

Adjusting and shimming the drive pinion

It is essential to adjust the position of the drive pinion before carrying out shimming of the taper roller bearings (7) (10) and (1) (2). Under no circumstances should this adjustment be modified without readjusting the shimming of the drive pinion bearings.

Using a press, insert cup (10) thrust against bearing carrier (13). Using a suitable fixture, insert cup (2) to thrust against housing (19). Screw in two diametrically opposed guide studs into the tapped bolt holes (11). Fit the carrier alone without shims (12). Alternatively and progressively, tighten the four bolts (11) to a torque of 100 - 130 Nm. Check that carrier (13) is in contact with the intermediate housing (19).

Using a press and an appropriate fixture, insert cone (7) to thrust against the drive pinion. Lubricate the taper roller bearings (7) (10) with transmission oil.

Temporarily fit the drive pinion without shims (3) but with thrust washer (4) placed between the bearing cone (1) and nut (18).

Pre-tighten the nut to a torque of 30 - 50 Nm using wrench ref. 3378118M1 and socket, ref. 3378119M1 taking care to correctly position the torque wrench. Turn the drive pinion several times to correctly seat the bearing cones in the cups. Check again the correct pre-tightening of nut (18).

Adjusting the position of the drive pinion

The thickness of shims (12) required to position the drive pinion is calculated as follows: E = Z � (X + Y) where:

E : Is the thickness of shims (12) to be fitted, tolerance � 0.05 mm.

Z : Is the nominal dimension between the rear face of the intermediate housing (19) and the axis of the differential crownwheel (22). This dimension is stamped inside the housing in the horizontal axis of the differential unit.

Y : Is the nominal dimension of the positioning of the drive pinion = 139.00

X : Is the dimension measured between the end of the drive pinion and the rear face of the intermediate housing. The drive pinion and the crownwheel are matched pairs with a number and letter engraved on each component.

Using a depth gauge, measure dimension "X". After having taken the measurement, use the formula to determine "E", the thickness of the shim(s) (12) to be fitted in order to correctly position the drive pinion.

Checks

- Temporarily refit the assembly fitted with the previously determined shims and measure dimension "X" again. Check that X + Y does in fact equal Z.

Remove the drive pinion and bearing carrier (13). On bearing carrier (13), refit the mechanism, the intermediate plates, the discs and unit (15). Refit the assembly on the intermediate housing (19).

- Carry out shimming of the drive pinion taper roller bearings.

Shimming taper roller bearings (7) (10) and (1) (2) of the drive pinion

On the drive pinion, slide the thickness of shims (3) required to obtain a provisional clearance of 0.10 mm to 0.15 mm maximum, in order to prepare P1 shimming. The thrust washer (4) must be placed against shoulder "E" of the drive pinion.

Lubricate bearing cup (2). Fit bearing cone (1). Using wrench, ref. 3378118M1 and socket, ref. 3378119M1, temporarily tighten nut (18) to a torque of 30 - 50 Nm. Place the index of the dial gauge on the tapered end of the pinion.

Pull strongly on the pinion via the front of the intermediate housing while alternately turning the pinion left and right to correctly seat the bearing cones in their cups.

With the assistance of another operator, set the dial gauge to zero.

In relation to the clearance measured, select a new thickness of shims (3) in order to obtain pre-loading: P1 = 0.04 mm to 0.10 mm. Loosen and take off nut (18). Slide the shims (3) selected during operation 132 between thrust washer (4) and bearing cone (1).

Degrease the threads of nut (18) as well as those of the drive pinion. Fit and definitively tighten the nut, its threads previously lightly smeared with Loctite 270, to a torque of 200 - 250 Nm. Manually check the rotation of the drive pinion. Lock the nut by bending its lock washer into the grooves of the pinion without breaking it, using an appropriate tool.