Backlash, Adjusting

BACKLASH, ADJUSTING
(Positioning ring gear in final drive housing)
^ The pinion must be adjusted and installed with shim S3,
^ Differential with shims "S1*" and "S2*" installed
- Install differential gear in axle housing, install cover and tighten all bolts to 25 Nm (18 ft. lbs.).
- Turn differential gear several times in each direction so tapered roller bearings settle.





- Install measuring tools.
- Use dial Indicator extension VW 382/10 (6 mm flat).
- Set VW388 measuring lever "a" to 60 mm.
- Determine play between gear teeth as follows:
- Turn ring gear to end of backlash travel and set dial indicator to zero (1 mm preload).
- Turn ring gear back and read and record backlash.
- Turn ring gear 90° and repeat measurement three more times.
- Add up four measurements and calculate average backlash.

Note: If during this measurement the individual values determined vary by more than 0.06 mm from each other, the installation of the ring gear or the ring gear and pinion set itself is not OK. Check the installation sequence. If necessary, replace the ring gear and pinion set.

Determining average backlash

Example:
1st Measurement = 0.28 mm
2nd Measurement = 0.30 mm
3rd Measurement = 0.30 mm
4th Measurement = 0.28 mm
Total (0.28 + 0.30 + 0.30 + 0.28) = 1.16mm

Average Backlash: 1.16/4 = 0.29 mm

Determining Shim Thickness "S2" (Correction Of Shim Thickness S2*)
S2 = S2* - average backlash + lift (constant value)
Lift = 0.15 mm





Example:
- Determine shims thickness from table provided.





The provided table shows available shims for "S2"

Determine shim thickness "S1"
S1 = S total - S2





Example:
- Determine shims thickness from table provided.





The provided table shows available shims for "S1"





Checking measurement
^ Drive pinion with "S3" installed
^ Differential with shims "S1*" and "S2*" installed
- Turn differential gear five times in each direction so tapered roller bearings settle.
- Measure backlash four times throughout rotation.
Specification: 0.12 - 0.22 mm

NOTES:
^ If backlash is not correct (0.12 - 0.22 mm), the adjustment procedure has to be repeated. The total shim thickness "S total" must not change.
^ The individual measurements must not deviate from each other by more than 0.06 mm.