Ring Gear, Adjusting
Drive Pinion and Ring Gear, Adjusting
General Information
• Careful adjustment of the drive pinion and ring gear is important for the service life and smooth running of the final drive. For this reason, the drive pinion and ring gear are matched together during manufacture, and checked to ensure a good mesh pattern and quiet running in both directions of rotation. The position of quietest running is found by moving the drive pinion in an axial direction and at the same time lifting the ring gear out of the zero-play mesh position by the amount necessary to maintain the backlash within the specified tolerance.
• The object of this adjustment is to reproduce the setting for the quietest possible running as obtained on the test machine in production.
• The deviation (or tolerance) "r", which is related to the master gauge "Ro" is measured for the final drive sets supplied as replacement parts and marked on the outer circumference of the ring gear. The final drive set (drive pinion and ring gear) may only be replaced together as a matched pair.
• Observe the general repair instructions for tapered roller bearings and shims.
• Maximum care and cleanliness are essential for achieving good results when performing repairs and taking measurements.
Ring Gear, Adjusting
Special tools, testers and auxiliary items required
• End measuring plate (VW385/17)
• Universal dial gauge bracket (VW387)
• Adjustable measuring lever (VW388)
• Crown wheel adjusting device (VW 521)
• Torque wrench (VAG1331) (or equivalent)
Adjusting Differential
It is necessary to readjust the ring gear when the following are replaced:
Rear axle housing
Final drive cover
Differential tapered roller bearings
Differential housing or
Drive pinion set
Adjustment overview => [ Adjustment Overview ] Adjustment Overview
• Differential tapered roller bearings are low-friction bearings. Therefore the frictional torque only has a limited use as a check. Correct adjustment is only possible by determining the total shim thickness "Stotal".
• Do not additionally oil new tapered roller bearings for frictional torque measurement. The bearings have already been treated with a special oil by the manufacturer.
Adjustment Shims S1 and S2, Determining Total Shim Thickness S Total
(Setting preload of tapered roller bearing for differential)
• Drive pinion removed!
• When the tapered roller bearing for the differential requires replacing the ring gear can be removed from the differential housing. The drive pinion need not be removed.
- Pull out flange shaft oil seal with lever.
- Remove differential tapered roller bearing outer races and take out shims => [ Differential ] Differential.
- Press outer race of left-hand tapered roller bearing for differential (housing side) with shim "S2*" (1.00 mm thick) into housing => [ Differential ] Differential.
• For measurement purposes a shim "S2" of 1.00 mm is initially inserted which will be designated "S2*" in the following. After determining the backlash "S2*" will be replaced by the correct "S2".
- Drive in outer race of right-hand tapered roller bearing for differential (final drive cover side) without shims => [ Differential ] Differential (install as far as it will go).
- Insert differential into housing. Ring gear is positioned on right side (cover side).
- Install cover and tighten bolts to 25 Nm.
- Install special tools (VW521/4) and (521/8) onto housing side in differential housing.
- Turn cover side of differential housing upward.
- Turn differential 8 turns in both directions so that tapered roller bearings settle.
- Place measuring plate (VW385/17) onto differential.
- Install measuring tools.
- A - = Dial gauge extension approx. 30 mm long
- B - = Hex bolt M8 x 45
- Place dial gauge extension on center of measuring plate (VW385/17).
- Set dial gauge (3 mm measuring range) to "0" with 2 mm preload.
- Lift differential without turning; read play on dial gauge and note.
• Measurement in following example: 0.50 mm
- If it is required to repeat measuring sequence turn differential 8 turns in both directions, so that tapered roller bearings settle.
Determining S Total
Shim S1, Determining Thickness
• The preliminary adjustment shim "S1*" will be replaced with the final shim "S1" after determining the backlash.
• The total shim thickness "Stotal" remains unchanged.
- Determine shim(s) as accurately as possible from table.
Frictional Torque, Measurement Check
• Drive pinion removed
• Differential installed with shims "S1*" and "S2*"
- Mount torque gauge 0 to 600 Ncm - A - onto differential.
- Read frictional torque.
Frictional torque specifications:
* run at least 50 km (30 miles)
• Differential tapered roller bearings are low-friction bearings. Therefore the frictional torque only has a limited use as a check. Correct adjustment is only possible by determining the total shim thickness "Stotal".
• Do not additionally oil new tapered roller bearings for frictional torque measurement. The bearings have already been treated with a special oil by the manufacturer.
• If the final drive set (drive pinion and ring gear) is being re-adjusted, the adjustment of the drive pinion should be performed now, and the adjustment checked => [ Drive Pinion, Adjusting ]. Drive Pinion, Adjusting
Adjusting Backlash
• Drive pinion with shim "S3" installed
• Differential with shims "S1*" + "S2*" installed
- Insert differential in final drive housing, install cover and tighten all bolts to 25 Nm.
- Turn differential 5 turns in both directions to settle tapered roller bearings.
- Assemble measuring equipment.
- Use dial gauge extension (VW382/10) (6 mm flat).
- Set Adjustable measuring lever (VW 388)to dimension "a" = 60 mm.
- Determine play between teeth flanks as follows:
- Turn ring gear until it makes contact with a tooth flank (end of backlash travel).
- Set dial gauge to "0" with 1 mm preload.
- Turn ring gear back until it lies against an opposite tooth flank (backlash).
- Read backlash and note value.
- Turn ring gear through 90° and repeat measurements a further 3 times.
Average Backlash, Determining
• Result: The average backlash is 1.16 ÷ 4 = 0.29 mm
• If the individual measurements differ by more than 0.06 mm from each other, the installation of the ring gear or the final drive set itself is not correct. Check installation, replace final drive set if necessary.
Shim S2, Determining Thickness
- Determine shim(s) as accurately as possible from table. Part numbers:
S2 Shim Table
* Using the shim tolerance variations it is possible to find the exact shim thickness required. Insert two shims if necessary.
Shim S1, Determining Thickness
- Determine shim(s) as accurately as possible from table. Part numbers:
S1 Shim Table
* Using the shim tolerance variations it is possible to find the exact shim thickness required. Insert two shims if necessary.
Performing Measurement Check
• Drive pinion with shim "S3" installed
• Differential with shims "S1" (cover side) + "S2" (housing side) installed
- Turn differential 5 turns in both directions so that tapered roller bearings settle.
- Measure backlash four times on circumference.
• Specifications: 0.12 to 0.22 mm
• If the backlash is outside the tolerance, the adjustments must be repeated. However, the total shim thickness "Stotal" must not be changed.
• The individual measurements must not differ by more than 0.06 mm from each other.