Ring Gear, Adjusting
Ring gear, adjusting
(Adjusting differential)
Special tools and equipment
^ VW 385/17 End measuring plate
^ VW 387 Universal dial gauge bracket
^ VW 388 Adjustable measuring lever
^ VW 521 Ring gear adjusting device
^ VAG 1331 Torque wrench
Not illustrated:
^ Dial gauge
It is necessary to readjust the ring gear when:
Rear axle housing, final drive cover, differential tapered roller bearings, differential housing or the drive pinion set are replaced.
Refer to Adjustment overview
Determining total shim thickness "S_total" (S1 plus S2)
(Adjusting differential tapered roller bearings)
^ Pinion shaft removed!
If only the tapered roller bearing for the differential is to be replaced, the ring gear can be removed from the differential cage. Then the pinion gear does not need to be removed.
- Pry out flange shaft oil seal with assembly lever.
- Remove differential tapered roller bearing outer race and take out shims.
- Press small tapered roller bearing outer race in together with a 1.00 mm thick shim onto stop in housing (S2 side).
- Install differential in housing.
The ring gear lies on the cover side.
- Install cover and tighten bolts to 25 Nm.
- Attach special tool to transmission housing side on differential housing.
- Turn final drive with cover side facing up.
- Turn differential 8 turns in both directions, so tapered roller bearings settle.
- Mount measuring tools.
- Place measuring plate VW 385/17 on differential.
A - dial indicator extension 30 mm
- Install bolt -B- M8 x 45.
- Place dial indicator extension on center of measuring plate VW 385/17.
- Set dial indicator gauge (3 mm measuring range) to zero with 2 mm preload.
- Move differential up and down (direction of arrow) without turning.
- Read play from dial indicator gauge.
Example:
0.50 mm
Determining S_total (S1 + S2)
"S_total"= dial gauge reading + preload
Note: If it is required that the measuring sequence be repeated, turn the differential 8 turns in both directions so the tapered roller bearings settle.
The specified bearing preload is obtained by adding a constant preload figure (0.30 mm) to the reading obtained (0.50 mm) and the thickness of the shim installed (1.00 mm).
Example:
- Install calculated shim thickness (1.80 mm in example) behind tapered roller bearing outer race in transmission housing (S2 side).
Note: Determine shims from parts Supplier.
Determining shim "S1"thickness
(Ring gear side)
Note: The temporary shim "S1" will be changed for the correct shim "S1" after calculating the backlash.
S1 = S_total - S2 (inserted shim)
Example:
S1 = 1.80 mm - 1.00 mm
S1 = 0.80 mm
Note:
^ Determine shims S1 and S2 from parts Supplier.
^ Different tolerances make it possible to select the exact thickness of shim(s) required.
- Determine and install shims S1 on ring gear side, and S2 opposite ring gear, installing 2 shims if necessary.
Adjusting backlash
^ Pinion shaft installed with S3
^ Differential: S_total (S1 + S2) installed in transmission housing.
- Install final drive cover and tighten bolts to 25 Nm.
- Turn differential several times in both directions so tapered roller bearings settle.
- Mount measuring tools.
Dial indicator extension VW 382/10 (6 mm flat)
- Set measuring lever VW 388 to dimension -a- = 60 mm
- Turn ring gear to stop. Set dial indicator gauge to zero with 1 mm preload -
- Turn ring gear back, read backlash and note reading.
- Repeat measurement three times, turning ring gear through 90° each time.
- Add four measured results and calculate average backlash -.
Calculating average backlash
Example:
1st measurement 0.28 mm
+ 2nd measurement 0.32 mm
+ 3rd measurement 0.32 mm
+ 4th measurement 0.28 mm
Total 1.20 mm
Average backlash = 1.20 mm + 4 = 0.30 mm.
If the individual measurements differ by more than 0.06 mm this means that the installation of the ring gear is not correct or that the ring gear and pinion themselves are faulty. Recheck the installation, and if necessary replace ring gear and pinion.
Determining shim "S2" thickness
(Opposite ring gear)
S2 = Inserted shim
- average backlash
- Lift (lift compensation for average backlash)
Lift=0.15mm
- Different tolerances make it possible to select the exact thickness of shim(s) required.
Table of shims
Note: Determine shims using parts catalog.
Determining shim "S1"thickness
(Ring gear side)
S1 = S_total - S2
Example:
S1 =1.80mm - 0.85mm
S1 = 0.95 mm
Table of shims
Note:
^ Determine shims using parts catalog.
^ Different tolerances make it possible to select the exact thickness of shim(s) required.
The final shim S1 replaces the temporary shim S1 after calculating the backlash.
- Determine and install shims S1 on ring gear side, and S2 opposite ring gear, installing 2 shims if necessary.
Check measurement
- Measure backlash four times around the circumference.
It must be 0.12...0.22 mm.
If the individual measurements differ by more than 0.06 mm this means that the installation of the ring gear is not correct or that the ring gear and pinion themselves are faulty. Recheck the installation, and if necessary replace the ring gear and pinion.