GPA40 rear axle - Rear PTO operation


The housing installed to the rear of the GPA40 rear axle contains all the rear mechanical power take-off components. These components rest on the tapered roller bearings, the bearing cups of which are on the rear PTO housing and its removable compartment and fitted freely and firmly respectively. 


Profile P of the 1000 rpm gear train teeth (driving and driven gears) differs according to the type of tractor and the transmission equipment fitted:
- Tractors installed with GTA1040 and GTA1540 tractor transmission without PTO Power Boost.
- Tractors installed with GTA1540 tractor transmission with PTO Power Boost.
The rear PTO is independent of the tractor transmission except for the Ground speed PTO version, which uses the tractor's forward speed for operation.
The Ground speed PTO is fitted to tractors as an option.

The rear PTO can be divided into four sections:

The clutch
The clutch is located on the upper PTO shaftline and at the front of the centre housing. It is supported by two ball bearings fitted in a support mounted on the centre housing.

The upper shaftline
The upper shaftline of the rear PTO transmits the engine speed to the driving gears located inside the rear housing of the PTO via the clutch and a series of three shafts. The tapered roller bearings supporting
the driving gear shaft are shimmed with a clearance using shim(s) inserted between the front bearing cup and the removable compartment.

The lower shaftline
The lower shaftline of the rear PTO is supported by two tapered roller bearings fitted respectively in the rear PTO housing and in the removable compartment. The tapered roller bearings are held in position by a nut screwed onto the front end of the output shaft. The preload shimming of the tapered roller bearings is carried out using shim(s) inserted between the front bearing cup and the removable compartment. The output shaft is sealed by a lip seal fitted into the rear PTO housing. The output shaft is fitted with an interchangeable end fitting which may be:
- of varying length;
- fitted with 6, 20 or 21 splines.
The specifications of the output shaft depend on the type of implement to be driven and on the rotational speed to be observed.


 The power take-off PTO brake
The rear PTO is fitted with a brake housed inside the rear housing opposite the 1000 rpm driven gear. The rear PTO brake gradually slows down the output shaft inertia until it stops completely when the rear PTO clutch is disengaged. It is also used to immobilise the gear trains (driving and driven gears) to prevent the "drag" effect.

Lubrication of the rear PTO (power take-off)  components

The clutch
The parts inside the rear PTO clutch are lubricated under pressure via a pipe located above and in front of the centre housing.

The upper shaftline
An external pipe carries the lubrication oil under pressure to the upper shaftline of the rear PTO. The flow of oil to the driving gears and the tapered roller bearings is controlled by two restrictors and an oil deflector located respectively in the rear housing of the PTO (power take-off) and in the upper shaftline.

The lower shaftline
The lower shaftline of the rear PTO is supplied with pressurised oil carried by a pipe to the front end of the output shaft. This oil lubricates the rear bearing and the splines of the output shaft driven gears.

The power take-off  brake
The PTO brake is not lubricated under pressure. Just the splashing of oil from the rear PTO housing is sufficient to lubricate the friction washer, which is in contact with the machined face of the 1000 rpm driven gear when the rear PTO (power take-off) line is locked.

Layout of the main components and kinematics

Tractors installed with GTA1040 tractor transmission



Tractors installed with GTA1540 tractor transmission



The lower fixture of the rear PTO housing on tractors installed with GTA1540 transmission is reinforced by fitting six 20 mm diameter screws instead of the four 16 mm diameter screws used on tractors fitted with GTA1040 transmission.

Housing interior: all rear PTO types

Parts list 
A - 540 E control mechanism
B - Interlock mechanism/adjustable sleeve assembly
C - 540 - 1000 rpm control mechanism
D - Upper PTO shaftline
E - Lower PTO shaftline
F - Rear housing of the PTO (power take-off)
G - GSPTO shaftline (optional)
H - Smooth ring
I - Shouldered ring
J - GSPTO control mechanism (optional)
K - Interchangeable end fitting
L - Transmission oil level gauge
M - Rear housing standard fixing (1040)
M - Rear housing reinforced fixing (1540)
N - Removable compartment
O - Fixing for linkage effort sensor
P - PTO brake mechanism and 1000 rpm driven gear
Q - Pin
R - Restrictor Ø 1 mm

2-speed PTO with coupler control


Parts list 
S - Power take-off driving shaft
T - 540 and 1000 rpm speed selection coupler
U - Output shaft with interchangeable end fitting
V - Driven gear train
W - Lubrication pipe
Z - Driving gear train

Kinematics 
The 540 and 1000 rpm driving gears of the upper shaftline have spur cut teeth and are constantly meshed with the respective 540 - 1000 rpm gears of output shaft U. They drive the output shaft at a speed of 540 or 1000 rpm depending on the position of selection coupler T.

3-speed PTO with coupler control


Parts list 
S - Power take-off driving shaft
T - 540 and 1000 rpm speed selection coupler
U - Output shaft with interchangeable end fitting
V - Driven gear train
W - Lubrication pipe
X - 540 E selection coupler
Z - Driving gear train

Kinematics 
The 540 - 1000 rpm and 540 E gears have spur cut teeth and are constantly meshed with the respective 540 - 1000 rpm and 540 E gears of output shaft U. They drive the output shaft at a speed of 540 - 1000 rpm or 540 E depending on the position of selection couplers T and X. The 540 E speed is an economic ratio. It is obtained via an additional gear and a coupler fitted to the front end of the driving gear train. When selection coupler X is engaged, two interlock mechanisms joined by an adjustable sleeve prevent selection coupler T from engaging. When a coupler is engaged, the interlock mechanisms lock the passive coupler in neutral at the control rod locking groove.

Ground Speed PTO with coupler control

The GSPTO is fitted to tractors as an option.


Parts list 
S - Power take-off driving shaft
T - GSPTO selection coupler
U - Output shaft with interchangeable end fitting
V - Driven gear (attached to gear Y by a screw)
In this configuration, the teeth of gear Y are passive. Only the gear hub acts as a transmission component between V and U.
W - Lubrication pipe
Y - Driven gear
Z - Driving gear

Kinematics 
The Ground Speed PTO driving and driven gears have spur cut teeth and are constantly meshed. They drive output shaft U at a speed proportional to the tractor's forward speed when selection coupler T is moved to the left. The GSPTO is activated when the 540 - 1000 rpm PTO is deactivated. The rotational movement of the Ground Speed PTO is transmitted via the rear axle pinion (crown wheel and pinion) and a gear train 4 wheel drive (4WD) at output shaft U via a driving shaft S and two gears Z and V.