Ring Gear, Adjusting

Ring Gear, Adjusting
(Adjusting differential)
Ring gear must be adjusted if any of the following have been replaced:
^ Transmission housing
^ Final drive cover
^ Differential tapered roller bearings
^ Differential housing
^ Final drive gear set (ring and pinion)

Determining total shim thickness "S_total" (S1 plus S2)
(Adjusting preload of differential tapered roller bearings)
^ Pinion removed!
- Pull out flange shaft oil seal with VW 681.
- Remove differential tapered roller bearing outer races and remove shims.
- Drive in tapered roller bearing outer races without shims.
- Install differential in housing without speedometer drive gear.
The ring gear is located on the left-hand side (cover side).
- Install cover and tighten bolts to 25 Nm (18 ft. lbs.).





- Mount special tool VW 521/4 and sleeve VW 521/12 on differential housing on transmission housing side.
- Place measuring plate VW 385/17 on differential.





- Set up measuring tools.
A- Dial indicator extension approx. 30 mm long
- Turn differential 8 turns in both directions, so that taper roller bearings can settle.
- Set dial indicator (3 mm range) to zero with 1 mm preload.
- Place dial indicator extension on center of measuring plate VW 385/17





- Move differential up and down (direction of arrow); take and record dial indicator reading.

Example:
1.42 mm


Determining "S_total" (S1 + S2)
"S_total" = dial indicator reading + preload





- Install shim of required thickness (1.77 mm in example) behind bearing outer race in transmission housing (S2 side).

Adjusting backlash
^ Pinion installed with shims S3 and S4
- Install differential S_total (S1 + S2) in transmission housing.
- Install final drive cover and tighten bolts to 25 Nm (18 ft. lbs.).
Turn differential several times in both directions so that tapered roller bearings can settle.





- Set up measuring tools.
^ Use extension VW 382/10 (6 mm square end).





- Set lever VW 388 to dimension -a- according to ring gear diameter:
- Turn ring gear to stop. Set dial indicator to zero.
- Turn ring gear back and read backlash.





- If pinion turns when ring gear is turned, use retainer 3177 (-A-) so backlash can be measured exactly.
The differential must then be installed so that cut-out for installing bevel gears faces pinion.
- Repeat measurement three more times, turning ring gear 1/4 turn (90°) each time.
- Add four reading together and calculate average backlash.
- With clamping bracket 3177 installed, turn differential 180�, reinstall and repeat measuring procedure.

Calculating average backlash

Example:





Average backlash = 3 36 mm ÷ 4 = 0.84 mm.

CAUTION: If the individual readings differ from one another by more than 0.06 mm, there is something wrong with the installation of the ring gear, or with the gear set itself.

Check all assembly operations and, if necessary replace the gear set.

Determining shim S2 thickness
(End opposite ring gear)
S2 = Inserted shim
- average backlash
+ Lift (constant value)

Lift = 0.15 mm





Example:


Determining shim S1 thickness
(Ring gear side)
S1 = S_total - S2

Example:
S1 = 1.92 mm -1.23 mm
S1 = 0.69 mm

Different shim tolerances make it possible to select the exact thickness of shim(s) required.

- Install correct shim S1 on ring gear side, and S2 on opposite side.

Note: Use two shims to achieve required thickness if necessary

Checking measurements
- Measure backlash three times around ring gear circumference.
^ Backlash must be 0.12 - 0.22 mm.