ZF Differential - Removing and install the drive pinion, adjusting the bevel gear distance



Remove the axle nose and take out the differential housing.
- Re-used bearing cups and cones must be matched pairs.
Loosen and take off nut (30) using a standard socket and holding clamp ref. 5870 240 002 from plate (28).
Remove the plate and recover washer (29).
Take out bolts (14) and remove ring (15).
Take out bolts (42) and extract flange (13).
Force off the drive pinion fitted with bearing cone (22) using a press and take it out through the rear of the housing.
Recover shim (9) and extract bearing cone (22) using a locally manufactured tool.
Extract the bearing cups (10) (21) from the housing and recover shim (23) that positions the drive pinion.
Drive the lip seal (12) off the flange (13).

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


Lightly smear the external diameter of seal (12) with Loctite 640 or its equivalent and insert it to within 8mm from the external edge of flange (13) using tool, ref. 5870 055 017 and handle, ref. 5870 260 002.

Adjusting the bevel gear distance


- If the crownwheel and drive pinion must be replaced, both parts must be replaced together. They are matched pairs with a number (e.g. 291) engraved both on the front face of the drive pinion and on the rim of the crownwheel.


- As with the backlash, the adjustment of the bevel gear distance is of firts importance. It ensures the reliability and the correct operation of the drive / crownwheel assembly.


- It is essential to first adjust the bevel gear distance and then carry out the shimming of the drive pinion.
- The adjustment of the bevel gear distance is carried out using a service tool made up from rod ref. 5870 500 001 and two bushes ref. 5870 500 010, held by the two halfbearings (18).

Adjustment 
The thickness of shim(s) necessary to correctly position the drive pinion is calculated using
the following formula: SP = A – (b + d + e)
SP : Thickness of shim(s) (23) to be fitted
A : Dimension measured between the housing (7) mating face and the top of the measurement axis
b : Radius of measurement axis
d : The nominal positioning dimension stamped into front face of drive pinion.
e : Thickness of bearings (21) (22)
r : Possible correction factor (e.g. –0.05) engraved on the forward face of the drive pinion.

Special point
- In the given example, the negative “r” value is subtracted from the nominal dimension “d”.
Measure dimension of A using tools, ref. 5870 500 001 and 5870 500 010.
Measure dimension “e” of bearing (21) (22) using a depth gauge.

Special point
- Take care to correctly seat bearing cone (22) in cup (21).
After having taken the measurements, use the previously stated formula to calculate the thickness of shim(s) required.
Using a press and an appropriate fixture, insert bearing cone (22) against the shoulder of the drive pinion.
Place the previously calculated thickness of shim(s) (23) in the housing. Insert the bearing cups (21) (10) using a press and an appropriate fixture.
Lubricate the bearing cones and cups and carry out the shimming of the drive pinion.
Install the pre-assembled drive pinion in the housing.

Shimming the drive pinion bearings
- The shimming of the drive pinion bearings requires calibrated ring ref. 5870 340 010.
- This ring has three mecanindus pins “G” fitted in opening holes 120° apart.


- Before using the calibrated ring, push the three pins as far out as they will go without losing them.
- The function of this tool is to measure the space between the shoulder of the drive pinion and the inner ring of bearing cone (22) after tightening to a preset tightening torque.
- The shim (9) to Install, will therefore be equal to the gap measured, in order to provide the correct preloading of the drive pinion bearings.
Slide the previously mentioned tool on to drive pinion (20), with pins G thrusting against the shoulder of the pinion.


Using an oven, only heat the inner ring of bearing cone (22) to 95° C. Slide the bearing rapidly on to the drive pinion in contact with the tool.

Provisionally Install the plate (28), washer (29) and nut (30) after having lubricated the threads of the drive pinion. Tighten nut (30) to a torque of:
- 2 Nm to 3 Nm for new bearings
- 1.5 Nm to 2 Nm for re-used bearings
Turn the drive pinion several times and check the tightening torque.
Take off the nut, washer and plate.
Drive off the drive pinion using a press and take it out through the rear of the housing. Recover the tool.
Measure dimension “X” on the tool. The thickness of the shim is equivalent
to measurement “X”.
- Measurement “X” is obtained by forcing the mecanindus pins into the disc of the tool applying the preset torque.
Install the drive pinion in the housing then slide on shim (9) as determined in operation, with chamfer C facing the drive pinion.
Using an oven, only heat the inner ring of bearing cone (11) to 95° C and definitively slide the bearing against the shim.
Lubricate the lips of seal (12). Lightly smear the mating face of flange (13) with housing (7) with Loctite 510 or its equivalent. Install the flange. Tighten bolts (42). Install ring (15) and tighten bolts (14).
Reinstall plate (28) and washer (29).
Degrease the threads of the drive pinion and the nut. Smear the threads of the nut with Loctite 270 or its equivalent and tighten to a torque of 350 Nm using a standard socket and the flange used during removal.
Install the differential housing and the axle nose.

Install the axle nose

Clean the mating faces on differential housing (7) and axle housing (1).
Smear the mating face of the differential housing with Loctite 510 or its equivalent, taking care that it does not enter the tapped holes.
Screw two diametrically opposed guide studs into the axle housing (optional).
Reinstall the housing using an appropriate fixture and position it according to the marks made when removing it.
Install and tighten bolts (33) to a torque of 190 Nm.

Install the swivel housings

Using a sling, reinstall the entire assembly of each swivel housing, taking care not to damage the dust cover and lip seal when introducing the universal drive shaft into the axle housing.
Install:
- the bearing cones and shims in their initial location
- the cover on the lower swivel pin
- the arm on the upper swivel pin
Tighten the cover and arm bolts to 190 Nm.
Install the grease nipples taking. Using a grease gun, moderately lubricate the swivel pin bearings.

Assembling ZF front axle and frame

Assemble the ZF front axle and bearings with the main stand.
Top up the oil level in the front axle housing and check the oil level in drive units.
Carry out a road test of the ZF front axle and the differential lock with limited slippage.
Check for the oil lightness of the mating face of the differential housing and plate. (28).