Audi Workshop Service and Repair Manuals

(Adjusting differential)

Repairs after which the crown wheel must be adjusted => adjustment overview on Page 39-44.

Special tools, testers and auxiliary equipment required

• ◆ Dial gauge extension VW 382/10
• ◆ Measuring plate VW 385/17
• ◆ Drive pinion clamp VW 386 A
• ◆ Universal dial gauge bracket VW 387
• ◆ Measuring lever VW 388
• ◆ Thrust plate VW 402
• ◆ Press tool VW 408 A
• ◆ Thrust piece VW 472/1
• ◆ Adjustment tool for crown wheel VW 521
• ◆ Torque gauge 0 ... 600 Ncm
• ◆ Dial gauge
• ◆ Dial gauge extension

Determining total shim thickness "Stotal" for shims "S1" + "S2"

(Setting preload of taper roller bearing for differential)

• ● Pinion shaft removed

Note:

If only the taper roller bearings for the differential are being renewed, the crown wheel can be removed from the differential housing. The pinion shaft does not then need to be removed.

• ‒ Remove seal and outer races of both taper roller bearings for the differential.
• ‒ Remove shims .

• ‒ → Knock taper roller bearing outer race (small) with shim "S2" into gearbox housing => Fig.39-33. For measurement purposes use a 1.20 mm thick "S2*" shim (2 shims of 0.60 mm).

Note:

For measurement purposes a shim "S2" with a thickness of 1.20 mm is initially inserted. It is referred to as "S2*" in the following. After determining the backlash "S2*" will be replaced by the correct "S2".

• ‒ → Press outer race for taper roller bearing without shim "S1" into cover for differential
  => Fig.39-37.
• ‒ Insert differential without drive wheel for speedometer sender -G22 into gearbox housing. The crown wheel is positioned on the left-hand side in front of the final drive cover .
• ‒ Install cover for differential with 4 bolts (25 Nm).
• ‒ Position gearbox so that cover for differential faces up.

• ‒ Turn differential 5 turns in both directions to settle the taper roller bearing.
• ‒ → Assemble measuring equipment, use a 30 mm dial gauge extension.
• ‒ Set dial gauge (3 mm measuring range) -A- to "0" with 2 mm preload.

Note:

The tip of the dial gauge must be positioned on centre of differential.

• ‒ Lift differential without turning; read off play on dial gauge and note.

• ● Measurement in following example: 0.62 mm

Notes:

• ◆ → Secure special tools VW 521/4 and VW 521/12 on right of differential (gearbox side) to lift differential.
• ◆ If the measurement has to be repeated, drive pinion must first be rotated another 5 turns in each direction to settle the taper roller bearing.

Determining thickness of shim "S1*"

Notes:

• ◆ The preliminary adjustment shim "S1*" will be replaced with the final shim "S1" after determining the backlash.
• ◆ The total shim thickness "Stotal" remains the same.

Measuring frictional torque (check)

Notes:

• ◆ Differential taper 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 taper roller bearings for frictional torque measurement. The bearings have already been treated with a special oil by the manufacturer.

• ● Pinion shaft removed

• ‒ → Fit torque gauge 0 ... 600 Ncm -A- onto differential.

•     B -    Socket

• ‒ Read off friction torque.

Frictional torque specified values:

Note:

If the final drive set is being re-adjusted, the adjustment of the pinion shaft should be performed now, and the adjustment should be checked .

Measuring backlash

(Position of crown wheel in gearbox housing)

• ● Pinion shaft with shims "S3" and "S4" installed

• ‒ Install differential.
• ‒ Turn differential 5 turns in both directions so that the taper roller bearings settle.

• ‒ → Secure dial gauge retainer VW 387 to the housing.
• ‒ Attach crown wheel adjusting device VW 521/4 and VW 521/12.
• ‒ Fit dial gauge with dial gauge extension VW 382/10 (6 mm flat).
• ‒ Adjust measuring lever VW 388 to dimension "a" = 67 mm (for 170 mm dia. crown wheel).
• ‒ Measure play between teeth flanks (backlash) as follows:
• ‒ Turn crown wheel until it makes contact with a tooth flank (end of backlash travel).
• ‒ Preload dial gauge to 2 mm and set to zero.
• ‒ Turn crown wheel back until lying against an opposite tooth flank (backlash).

• ‒ Read off backlash and note value.
• ‒ Turn crown wheel through 90o and repeat measurements a further 3 times.

Notes:

• ◆ → If drive pinion rotates when the differential is turned, fit clamp VW 386 A so that backlash can be measured accurately.
• ◆ Loosen the clamp in order to turn the crown wheel.

Determining average backlash

• ‒ Add the four measured values together and divide by four.

• ● Result: The average backlash is 1.16 divided by 4 = 0.29 mm

Note:

If the individual measurements differ by more than 0.06 mm this means that the installation of the crown wheel is not correct or that the final drive set itself is defective. Check installation, replace final drive set, if necessary.

Determining thickness of shim "S2"

• ‒ Determine shim(s) as accurately as possible from table. Part numbers

=> Parts List

The following shims are available for "S2"

    1)    Using the shim tolerance variations it is possible to find the exact shim thickness required, insert two shims if necessary.

Determining thickness of shim "S1"

• ‒ Determine shim(s) as accurately as possible from table. Part numbers

=> Parts List

The following shims are available for "S1"

    1)    Using the shim tolerance variations it is possible to find the exact shim thickness required, insert two shims if necessary.

→ Check measurement

• ‒ After installing shims "S1" and "S2", turn the differential 5 turns in both directions so that the taper roller bearings settle.
• ‒ Measure backlash four times on circumference.
• ‒ Specified value: 0.12 ... 0.22 mm

Notes:

• ◆ If the backlash is beyond the tolerance, the adjustments must be repeated. The total shim thickness "Stotal" must not be changed.
• ◆ The individual measurements must not differ by more than 0.06 mm from each other.