Differential: Service and Repair
Replacing differential
Preliminary work
1. Remove transmission.
2. Use engine support 9589 to secure the transmission on the assembly support.
3. Drain transmission oil.
Determining current condition
Determining tooth backlash
Information
If the adjusting shims are severely deformed, they must be replaced with new shims of the same thickness.
1. Lever off halfshaft flanges.
Levering off halfshaft flange
2. Lever out sealing rings for halfshaft flanges.
Levering out sealing ring
3. Measure tooth backlash.
3.1. Set up measuring tools according to - Measuring tooth backlash.
Measuring tooth backlash
1 - Adjustable measuring lever VW 388
2 - Bush 9145
3 - Adjusting device VW 521/4
4 - Dial gauge holder VW 387
5 - Dial gauge Nr.136 Pos.2
a - - Adjustment value: 68 mm
3.2. Set dial gauge Nr.136 Pos.2 to 0 with 1 mm preload and measure tooth flank Z1.
Example:
Measured result: Z1 = 0.11 mm
3.3. Remove measuring tools, turn crown wheel by 90° and repeat the measurement.
Example:
Measured result: Z2 = 0.09 mm
3.4. Perform the measurement a total of four times and calculate the average ZGes of the four measured results.
ZGes = Z1 + Z2 + Z3 + Z4/4
Example:
Measured result 1: Z1 = 0.11 mm
Measured result 2: Z2 = 0.09 mm
Measured result 3: Z3 = 0.10 mm
Measured result 4: Z4 = 0.10 mm
Average: ZGes = Z1 + Z2 + Z3 + Z4/4 = (0.11 mm + 0.09 mm + 0.10 mm + 0.10 mm)/4 = 0.10 mm
Determining bearing pre-load
Information
If the adjusting shims are severely deformed, they must be replaced with new shims of the same thickness.
1. Remove differential cover.
1.1. Unscrew 14 screws and remove the cover, using a rubber hammer if necessary
Cover
2. Remove traces of sealant from the transmission housing and cover and clean the parts.
3. Remove crown wheel.
3.1. Remove differential.
3.2. Carefully clamp the differential in a vice.
3.3. Unscrew 16 screws.
3.4. Remove crown wheel using a rubber hammer or aluminum mandrel.
Crown wheel
4. Remove outer bearing ring from the transmission housing.
4.1. Insert internal puller internal puller Nr.108 Pos.7 into the transmission housing.
4.2. Remove outer bearing ring with adjusting shim from the transmission housing.
Outer bearing ring
5. Measure the adjusting shim.
Example:
Measured result: SG = 1.48 mm
Measuring the adjusting shim
6. Insert a thinner adjusting shim into the transmission housing.
6.1. Take the thinnest available adjusting shim from the set and insert it into the transmission housing.
Example:
Thickness of the new adjusting shim: SGd = 1.06 mm
7. Fit old outer bearing ring.
7.1. Drive the old outer bearing ring into the transmission housing using pressure piece 9708/6.
Fitting outer bearing ring
8. Remove outer bearing ring from the differential cover.
8.1. Place differential cover on the transmission.
8.2. Insert internal puller internal puller Nr.108 Pos.7 into the transmission cover.
8.3. Remove inner bearing ring with adjusting shim from the transmission cover.
Outer bearing ring
9. Measure the adjusting shim.
Example:
Measured result: SD = 1.25 mm
Measuring the adjusting shim
10. Insert a thinner adjusting shim into the transmission cover.
10.1. Take the thinnest available adjusting shim from the set and insert it in the transmission cover.
Example:
Thickness of the new adjusting shim: SDd = 0.94 mm
11. Fit old outer bearing ring.
11.1. Drive the old outer bearing ring into the transmission housing using pressure piece 9708/6.
Fitting outer bearing ring
12. Fit the differential.
12.1. Insert differential into transmission.
12.2. Fit transmission cover and secure with four screws.
13. Measure differential backlash.
13.1. Set up measuring tools according to - Measuring backlash.
Measuring backlash
1 - Dial gauge holder VW 387
2 - Dial gauge Nr.136 Pos.2
3 - 50-mm gauge block VW 385/17
4 - Adjusting device VW 521/4 with bushing 9145
13.2. Dial gauge Nr.136 Pos.2 must be set to 0 with 1 mm pre-load.
13.3. Press the differential upward with adjusting device VW 521/4 and read the backlash off the dial gauge Nr.136 Pos.2.
Example:
Measured result: Backlash = 0.44 mm
13.4. Remove measuring tools.
14. Calculate the bearing pre-load.
14.1. Calculation of the original total shim thickness: SG + SD = SGes
Example:
1.48 mm + 1.25 mm = 2.73 mm
14.2. Calculation of the -too thin- total shim thickness: SGd + SDd = SGesd
Example:
1.06 mm + 0.94 mm = 2.00 mm
14.3. Calculation of the original bearing pre-load: SGes - SGesd - Sp = V
Example:
V = 2.73 mm - 2.00 mm - 0.44 mm = 0.29 mm
Installing new differential
Installing taper roller bearings
1. Drive two new taper roller bearings onto new differential using drift P264b.
Fitting taper roller bearings
Determining new total shim thickness
Information
If the adjusting shims are severely deformed, they must be replaced with new shims of the same thickness.
1. Remove outer bearing ring from the transmission housing.
1.1. Insert internal puller internal puller Nr.108 Pos.7 into the transmission housing.
1.2. Remove outer bearing ring from the transmission housing.
1.3. The thin adjusting shim remains in the transmission housing.
Outer bearing ring
2. Drive new outer bearing ring into the transmission housing.
Drive new outer bearing ring into the transmission housing with pressure piece 9708/6.
Fitting outer bearing ring
3. Remove outer bearing ring from the transmission cover.
3.1. Place transmission cover on transmission.
3.2. Insert internal puller internal puller Nr.108 Pos.7 into the transmission cover.
3.3. Remove inner bearing ring from the transmission cover.
3.4. The thin adjusting shim remains in the differential cover.
Outer bearing ring
4. Drive new outer bearing ring into differential cover.
Drive new outer bearing ring into the differential cover using pressure piece 9708/6.
Fitting outer bearing ring
5. Insert new differential with new taper roller bearings into the transmission.
5.1. Insert differential into transmission.
5.2. Put on transmission cover and fasten with four screws.
6. Measure differential backlash.
6.1. Set up measuring tools according to - Measuring backlash
Measuring backlash
1 - Dial gauge holder VW 387
2 - Dial gauge Nr.136 Pos.2
3 - 50-mm gauge block VW 385/17
4 - Adjusting device VW 521/4 with bushing 9145
6.2. Dial gauge Nr.136 Pos.2 must be set to 0 with 1 mm pre-load.
6.3. Press the differential upward with adjusting device VW 521/4 and read the backlash off the dial gauge Nr.136 Pos.2.
Example:
Measured result: Spn = 0.42 mm
6.4. Remove measuring tools.
7. Calculate new total shim thickness SGesn.
SGesn = SD + SG. Sp + Spn
Example:
SGesn = 1.25 mm + 1.48 mm. 0.44 mm + 0.42 mm = 2.71 mm
Installing crown wheel
1. Remove differential cover.
2. Remove differential.
3. Fit crown wheel on differential.
3.1. Place crown wheel on differential.
3.2. Put in 4 screws and pull the crown wheel in until it contacts the seat.
3.3. Carefully clamp the new differential in a vice.
3.4. Screw in the remaining 12 screws.
3.5. Tighten the 16 screws.
Crown wheel
Installing outer bearing ring in transmission housing
Information
If the adjusting shims are severely deformed, they must be replaced with new shims of the same thickness.
1. Remove outer bearing ring from the transmission housing.
1.1. Insert internal puller internal puller Nr.108 Pos.7 into the transmission housing.
1.2. Remove outer bearing ring with adjusting shim from the transmission housing.
Outer bearing ring
Information
A shim of the same thickness already permits an adjustment of the tooth backlash that is as exact as possible at this point.
2. Insert an adjusting shim SGn of the same thickness as the original adjusting shim SG into the transmission housing.
Example:
SG = SGn = 1.48 mm
3. Drive new outer bearing ring into the transmission housing.
Drive new outer bearing ring into the transmission housing with pressure piece 9708/6.
Fitting outer bearing ring
Installing outer bearing ring in differential cover
1. Remove outer bearing ring from the transmission cover.
1.1. Place transmission cover on transmission.
1.2. Insert internal puller internal puller Nr.108 Pos.7 into the transmission cover.
1.3. Remove inner bearing ring with adjusting shim from the transmission cover.
Outer bearing ring
2. Calculate thickness of the new adjusting shim SDn.
SDn = SGesn - SGn
Example:
SDn = 2.75 mm - 1.48 mm = 1.27 mm
3. Insert a new adjusting shim of the corresponding thickness into the transmission cover.
4. Drive outer bearing ring into differential cover.
Drive outer bearing ring into the differential cover using pressure piece 9708/6.
Fitting outer bearing ring
Checking tooth backlash
1. Insert differential into transmission and check whether there is tooth backlash.
Information
The differential cover may only be fitted if there is tooth backlash and no compression between the bevel gear and crown wheel.
2. Fit differential cover and secure with four screws.
3. Measure tooth backlash.
3.1. Set up measuring tools according to - Measuring tooth backlash
Measuring tooth backlash
1 - Adjustable measuring lever VW 388
2 - Bushing 9145
3 - Adjusting device VW 521/4
4 - Dial gauge holder VW 387
5 - Dial gauge Nr.136 Pos.2
a - - Adjustment value: 68 mm
3.2. Dial gauge Nr.136 Pos.2 must be set to 0 with 1 mm pre-load.
3.3. Remove measuring tools, turn crown wheel by 90° and repeat the measurement.
3.4. Perform the measurement a total of four times and calculate the average of the four measured results.
The average of the four measurements must be between 0.06 mm and 0.11 mm and must not deviate by more than 0.03 mm from the original tooth backlash. Furthermore, no individual measurement may deviate by more than 0.04 mm from the original tooth backlash. If one of the specified conditions is not met, the adjusting shim measurement must be recalculated. The tooth backlash must then be checked again. The total shim thickness SGesn must not be changed.
Assembling transmission
1. Remove differential cover.
2. Coat differential cover and differential housing with Loctite 574 sealant.
3. Fit differential cover, screw in and tighten screws.
4. Drive sealing ring into differential cover.
4.1. Screw M10 x 30 hexagon-head bolt into side B of pressure piece 9734.
Bolt in special tool
4.2. Apply a thin coat of Vaseline on the outer edge and sealing lip of the sealing ring, and place the sealing ring on side A of pressure piece 9734.
Sealing ring on special tool
4.3. By tapping on the hexagon-head bolt using a hammer, drive the sealing ring completely into the differential cover with the pressure piece 9734.
Tapping in sealing ring
5. Install left halfshaft flange.
6. Drive sealing ring into differential cover.
6.1. Screw M10 x 30 hexagon-head bolt into side A of pressure piece 9734.
Bolt in special tool
6.2. Apply a thin coat of Vaseline on the outer edge and sealing lip of the sealing ring, and place the sealing ring on side B of pressure piece 9734.
Sealing ring on special tool
6.3. By tapping on the hexagon-head bolt using a hammer, drive the sealing ring completely into the differential with the pressure piece 9734.
Tapping in sealing ring
7. Install the right halfshaft flange.
Subsequent work
1. Install transmission.
2. Fill with transmission oil.