Differential with standard bevel gear and multidisc lock


The tractors are equipped with an identical centre housing. The intermediate housing differs depending on the type of gearbox.

Specifications

Model tractors
- Heavy Duty gearbox
- narrow intermediate housing

Model tractors
 - AG 150 Full Powershift gearbox
- wide intermediate housing

Model tractors
- AG 250 Full Powershift gearbox
- wide intermediate housing (hypoid version)

Some tractors are fitted with a standard bevel gear and either a multidisc or hydromechanical differential lock (depending on version).

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 carrier (13). The bearing cone (1), mounted free on the drive pinion, allows to fit shims (3) required for shimming. The crownwheel is fastened to the differential housing by rivets. The differential assembly rotates on two taper roller bearings supported by two lateral carriers centred by bushes (25) (40) and fixed by bolts to the housing. The differential assembly is formed by two halves holding four planetary gears and two sun gears. The drive pinion, which bears the 4 WD drive pinion (17) (if fitted), is located in the intermediate housing. The adjustment of its position is carried out by shims (12) fitted between the differential lock carriers, the bearings (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 pre-loading via shimming of the differential assembly is carried out via shims (55) placed between bearing cone (54) and the left-hand carrier (38). Backlash of the drive pinion and the crownwheel is obtained by using shims (59) inserted between cup (32) and the differential half-housing (23).

Differential lock
The multidisc lock system, located on the left-hand side of half-housing (23), comprises:
- a unit (46) housing the discs (49) and intermediate plates (48),
- a hub (53) integral via splines with the left-hand trumpet input sun gear,
- a cover (52) made up by piston assembly (58) and supported by taper roller bearings (54) (57).
The piston chamber lodged in the cover communicates with a channel in the left-hand carrier, allowing (17 bar) low pressure to act upon the piston. Two seal rings (56) ensure the oil tightness of the circuit.

Operation

Clutched position
When the differential lock solenoid valve is activated, the pressure flows through the channels of carrier (38) and cover (52) and enters piston chamber (58). The piston compresses the intermediate plates (48) and discs (49) integral respectively via stops and splines in lock unit (46) and hub (53). In this ‘clutched’ position, the input sun gears of the right-hand 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.

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 (if fitted)
(18) Nut (19) Intermediate housing (20) Deflector (22) Crownwheel (23) Differential half-housing (24) Rivets (25) Centring bush (26) Bolt (27) Right-hand carrier (28) Spherical washer (29) Planetary gear
(30) Sun gear (31) Bearing cone (32) Bearing cup (33) Brace (34) O’rings (35) Shouldered bush (36) Fixed dog (37) O’ring (38) Left-hand carrier (39) Bolt (40) Centring bush (41) Bolt (42) Transfer tube
(43) O’ring (44) Union (45) Centre housing (46) Differential lock disc unit (47) Bolt (48) Intermediate plates (differential lock) (49) Discs (50) O’ring (51) O’ring (52) Cover (53) Hub (54) Bearing cone (55) Shims (56) Seal ring (57) Bearing cup (58) Piston (59) Shim(s) (60) Rivet (61) Shouldered bush


Removing and refitting the carriers

Left-hand carrier 
It is possible to carry out maintenance on carrier (38) and seal rings (56) 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 (42). Remove the brake piston. Remove bolts (39) from the left-hand carrier as shown in Figure. Place two diametrically opposed guide studs "G" on the housing, their ends resting against cover (52) of the lock unit.


Extract the carrier through the tapped holes and using two bolts "V", take it off and recover cone (54) and shim(s) (55). The guide studs "G" hold and centre the differential assembly (36) in the housing.


Do not unscrew the guide studs in order not to throw off centre the assembly and damage the seal rings (56) during refitting of the carrier.

Refitting
Check for the presence of centring bush (40), the correct positioning of shim(s) (55) and bearing cone (54). Check that the seal rings (56) 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 when refitting the carrier. Fit new O’rings (34) (37).
Slide the carrier onto the guide studs "G" and alternately and uniformly tighten the four bolts (39) 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 (42) in carrier (38). Screw in and position union (44). Refit the brake piston. Check the oil tightness of seal (34) on carrier (38). Refit the left-hand trumpet housing.

Right-hand carrier
The access to the right-hand carrier (27) is similar to that of the left-hand carrier (38).

Removal
- Take out bolts (26) and place diametrically opposed guide studs in the housing, their end resting against the half-housing (23).
- Extract and remove the carriers by inserting the two bolts "V" through the tapped holes and take it off.

Refitting
- Check for the presence of the centring pin (25) and O’ring (34).
- Tighten uniformly and alternately the four bolts (26) 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 (34) on carrier (27).