GPA40 rear axle - Operation


The GPA40 tractor rear axle comprises four housings:
the centre housing
On the inside, it supports:
- the rear differential assembly and ring gear;
- the pinion;
- the PTO clutch

On tractors equipped with GTA1540 transmission, the sensor located at the top of the centre housing, towards the front, measures the engine speed at the PTO clutch input;
- the 4WD clutch;
- the hand brake control mechanism;
- the annular pistons and main brake discs

On tractors equipped with GTA1540 transmission (50 kph), the braking surface of the annular pistons and brake discs is optimised. A mechanical device controls the return of the annular pistons and cancels out any play resulting from the friction of the discs on the annular pistons when braking;
- the Park Lock device (depending on option);
- the creeper unit control mechanism (optional).
On the outside, it supports:
- the right and left-hand hydraulic cover plates;
- the supports fitted to the upper part of the centre housing holding the support and linkage arms.

On tractors equipped with GTA1540 transmission, the centre housing is reinforced where the linkage support and rear PTO housing are attached. This is the case regardless of the tractor speed (40 or 50 kph).
the PTO housing
It supports:
- all variants of the PTO transmission;
- the PTO brake.
the right and left-hand trumpet housings
These are fitted to either side of the centre housing and house the rear wheel drive system.

On tractors equipped with GTA1540 transmission, the number of tapped holes used to attach the trumpet housing to the centre housing differs according to the type of trumpet housing:
- Normal Duty and Heavy Duty trumpet housings: 9 tapped holes;
- sealed Heavy Duty trumpet housings: 15 tapped holes;
- trumpet housings with composite final drive: 15 tapped holes.
The trumpet housings are sealed by special seals located:
- for Heavy Duty and sealed Heavy Duty trumpet housings: in the trumpet housings and between the trumpet housings and centre housing;
- for Normal Duty trumpet housings: between the trumpet housings and centre housing;
- for trumpet housings with a composite final drive: between the trumpet housings and centre housing.

Layout of the main components

2-speed PTO version


Tractors fitted with GTA1040 transmissionParts list 
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crown wheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option) (7) PTO clutch (8) 540-1000 rpm driven gears (9) 4WD clutch (10) Park Lock device (depending on option) (12) Interchangeable end fitting (13) 540-1000 rpm driving gears


Tractors fitted with GTA1540 transmissionParts list 
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crownwheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option)  (7) PTO clutch (8) 540-1000 rpm driven gears (9) 4WD clutch (10) Park Lock device (depending on option) (12) Interchangeable end fitting (13) 540-1000 rpm driving gears

3-speed PTO version


Tractors fitted with GTA1040 transmissionParts list 
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crown wheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option). (7) PTO clutch
(8) 540 E driven gear (9) 4WD clutch (10) Park Lock device (depending on option) (12) Interchangeable end fitting (13) 540 E driving gear


Tractors fitted with GTA1540 transmissionParts list 
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crownwheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option). (7) PTO clutch (8) 540 E driven gear (9) 4WD clutch (10) Park Lock device (depending on option)
(12) Interchangeable end fitting (13) 540 E driving gear

Ground Speed PTO version (GSPTO)


Tractors fitted with GTA1040 transmissionParts list 
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crown wheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option). (7) PTO clutch (9) 4WD clutch (10) Park Lock device (depending on option) (11) GSPTO (depending on option)
(12) Interchangeable end fitting


Tractors fitted with GTA1540 transmission (40 kph only)Parts list  
(1) Lubrication pipes (PTO clutch, hand brake discs, PTO transmission and 4WD clutch) (2) Centre housing (3) PTO housing (4) Crownwheel and pinion and rear differential (5) Hand brake mechanism (6) Creeper unit control mechanism (depending on option) (7) PTO clutch (9) 4WD clutch (10) Park Lock device (depending on option) (11) GSPTO (40 kph only) (12) Interchangeable end fitting