GPA40 rear axle – Pinion


Construction
The crownwheel and pinion, driven by the gearbox output shaft, drives the rear axle. The helical pinion is supported by two tapered roller bearings fitted opposite one another. The bearing cone (7) is force fitted onto the pinion. The bearing cup (2) is fitted tightly into the cover plate (13). The bearing cup (10) is fitted tightly into the hand brake unit. The bearing cone (1), freely mounted on the pinion, allows the fitting of shims (3) required for shimming. The pinion supports the 4WD drive gear (17). Its position can be adjusted using the shim(s) (12) fitted between the centre housing compartment and the hand brake unit (15). The preload on the tapered roller bearings is obtained using the shim(s) (3) fitted between the bearing cone (1) and the thrust washer (4). On tractors fitted with GTA1040 transmission, the pinion fitting and adjusting principle is the same for the three current types of differential:
- 5" hydromechanical differential;
- 5" multidisc differential;
- 7" multidisc differential.

On tractors fitted with GTA1540 transmission, the pinion fitting and adjusting principle is the same for the two current types of differential:
- 5" multidisc differential;
- 7" multidisc differential.

Lubrication
The oil is directed via a pipe to the axial channel and the radial holes of the pinion to lubricate the hand brake mechanism and the tapered roller bearings. The pipe is connected to the hydraulic manifold located above the centre housing.

Parts lists 
(1) Bearing cone (2) Bearing cup (3) Shim(s) (4) Thrust washer (5) Allen screws (6) Hand brake mechanism (7) Bearing cone (8) Allen screw (9) Pinion (10) Bearing cup (11) Washer (12) Shim(s) (13) Hand brake unit cover plate (14) Locating pin (15) Hand brake unit (17) 4WD drive gear (18) Nut
(45) Centre housing (62) Lubrication pipe

Legend
1 - GTA1040 transmission
2 - GTA1540 transmission
A Details
B Details
L Lubrication

Removing and refitting the pinion/hand brake unit assembly, removing and refitting the pinion

Disconnect the tractor between the gearbox and the rear axle.
Remove the right-hand hydraulic cover plate (LS 110 l/min hydraulics).
Remove the left-hand hydraulic cover plate (LS 110 l/min hydraulics).
Remove the rear power take-off clutch.


Remove the 4WD shaft and its clutch:
1 - GTA1040 transmission
2 - GTA1540 transmission
Remove the creeper unit control mechanism (if fitted).
Remove the circlip (5) and the thrust washer (2). Visually note the position of the shim(s) (6) and remove it/them. Remove the 4WD gear (17), sliding it along the pinion.

Removing the pinion/hand brake unit assembly
The pinion/hand brake unit assembly must be removed in order to work efficiently on the pinion. Loosen and immobilise the nut (18) using wrench ref. 3378118M1.


Using special socket ref. 3378119M1, turn the pinion clockwise to unlock the nut without unscrewing it completely. The nut is not removed completely until the hand brake unit is on the workbench for stripping. Unscrew the eight M12 hexagonal head screws (8). Remove their washers (11).
Unscrew the M20 screw (1) from the hand brake actuator lever.


Unscrew the two M12 Allen screws (5) that attach the hand brake unit (15) to the centre housing compartmentSlide tool ref. 3378465 M1 onto the pinion splines. Moderately tighten the tool's three screws V in groove R of the pinion.


Sling the tool using a makeshift handling bar and a suitable lifting device.
Carefully pull the pinion/hand brake unit assembly forwards and release it from the centre housing.


Recover the shims (12) (internal diameter approx. 175 mm) on the hand brake unit assembly. The shims inserted between the hand brake unit and the centre housing compartment are used for adjusting the taper distance.
Separate the sling and tool from the pinion/hand brake unit assembly.

Disassembling the pinion
Place the pinion/hand brake unit assembly vertically on the workbench.
Completely unscrew the nut (18) and discard itRemove:
- the tapered roller bearing cone (1);
- the shim(s) (3);
- the thrust washer (4), marking its position.


Remove the cover plate (13) and the hand brake mechanism (6)Remove the pinion, separating it from the hand brake unit (15). If necessary, extract the tapered roller bearing cone (7) from the pinion. Remove:
- the bearing cup (2) from the cover plate (13)
- the locating pin (14) from the hand brake unit (15).

Reassembling the pinion
The shimming with preload on the pinion's tapered roller bearings and the adjustment of the pinion/hand brake unit assembly position must be checked after one or more of the following parts are replaced:
- the centre housing;
- the pinion
- the head bearing (tapered bearing cone (7) and the cup (10));
- the hand brake unit (15);
- the unit cover plate (13);
- the end bearing (tapered bearing cone (1) and cup (2)).
Clean and check all components. Replace those that are defective.
If disassembled, use a press and a suitable fixture to fit the tapered roller bearing cone (7) against the pinion shoulder. Fit the tapered roller bearing cone (10) against the shoulder of the hand brake unit. Check that the elements are properly supported by their respective bases. Place the hand brake unit (15) vertically on the workbench, having fitted the pinion beforehand. Reassemble the hand brake mechanism inside the unit (15). Fit the tapered roller bearing cup (2) against the cover plate shoulder (13). Fit the cover plate (13) after checking that the locating pin (14) is present.


On the pinion, slide the thrust washer (4) against shoulder E together with the shim(s) (3) used to preload the tapered roller bearings. The shim(s) (3) required for shimming by preloading the tapered roller bearings (1) (2) and (7) (10) must be inserted between the thrust washer (4) and the tapered roller bearing cone (1).
Fit the tapered roller bearing cone (1) after lubricating the cone with clean transmission oil. Tighten the new nut (18) without locking it. If necessary, carry out the shimming with preload on the pinion tapered roller bearings and the adjustment of the position of the pinion/hand brake unit assembly. The new nut (18) will be definitively locked when the pinion/hand brake unit assembly (15) is refitted to the centre housing.

Refitting the pinion/hand brake unit assembly
Clean and check all components. Replace those that are defective.
Position the shim(s) (12) on the fitting area of the hand brake unit (15).
Using tool ref. 3378465M1, refit the pinion/hand brake unit assembly against face F of the centre housing compartment. During the refitting process, refit the hand brake actuator lever at the same time.


Press the hand brake unit towards the centre housing compartment, in preparation for fitting. Align the three fixing holes on the hand brake unit with the compartment holes by screwing a guide stud into a tapped hole located at the top of the centre housing. Clean the thread of the screws (5) (8) and lightly smear with Loctite 242 or equivalent. Screw in the Allen screws (5).
Screw in the hexagonal head screws (8) fitted with their washers (11) while removing the guide stud at the same time.


Tighten the diametrically opposed screws (5) (8) uniformly and step-by-step to a tightening torque of 100-130 Nm. This tightening method ensures that the hand brake unit (15) is fitted gradually and smoothly into the centre housing compartment and that the shim(s) (12) are applied appropriately.
Adjust the hand brake mechanism (see chapter 6).

Final steps
Degrease the threads of the new nut (18) and the pinion.
Lightly smear the thread of the nut with Loctite 270 or equivalent. Lock the nut with wrench ref. 3378118 M1 . Using socket ref. 3378119 M1, turn the pinion anti-clockwise to a tightening torque of 200-250 Nm. Ensure that the torque wrench is properly positioned in order to obtain the correct tightening torque for the nut. Remove tools.


Using a suitable punch, lock the nut by bending its collar, without breaking it, into the three pinion grooves. Slide the 4WD gear (17) over the pinion splines. Fit the following, observing the correct fitting order:
- the shim(s) (6) then
- the thrust washer (2) then
- the circlip (5).
Check the axial clearance of the 4WD gear (17): it should be between 0 and 0.55 mm. As far as possible, shim to the minimum tolerance.
Refit:
- the left-hand hydraulic cover plate (LS 110 l/min equipment).
- the right-hand hydraulic cover plate (LS 110 l/min equipment).
- the creeper unit control mechanism (if fitted).
- the 4WD clutch and its shaft.
- the power take-off clutch.
Reconnect the tractor between the gearbox and the rear axle.
Carry out a road test. Check tightness of:
- Mating faces;
- Hydraulic unions