Audi Workshop Service and Repair Manuals

(Adjusting differential)

Repairs after which the crown wheel must be adjusted => adjustment overview on Page 39-168.

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 special oil by the manufacturer.

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

(Setting preload of taper roller bearing for differential)

• ● Drive pinion removed or crown wheel dismantled from differential housing

• ‒ Lever out seals for flange shaft using a suitable lever.
• ‒ Remove outer races of differential taper roller bearings and remove shims .

• ‒ Drive in left taper roller bearing outer race for differential (housing side) with shim "S2" into final drive housing => Fig.39-142. For measurement purposes use a 1.00 mm thick "S2*" shim (2 shims, 1 of 0.80 mm and 1 of 0.20 mm).

Note:

For measurement purposes a shim "S2" with a thickness of 0.04 in 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 in outer race for right taper roller bearing for differential (cover side) without shim in up to stop => Fig.39-134.
• ‒ Insert differential into housing. The crown wheel is positioned on the right side (cover side).

• ‒ Fit cover and tighten bolts to 25 Nm.
• ‒ → Install special tools VW 521/4 and 521/8 onto housing side in differential housing.
• ‒ Turn cover side of differential housing upwards.

• ‒ Turn differential 5 turns in both directions to settle the taper roller bearing.
• ‒ Place measuring plate VW 385/17 onto differential.
• ‒ → Fit measuring tools.

•     A -    Dial gauge extension approx. 30 mm long
•     B -    Hexagon bolt M8 x 45

• ‒ Position dial gauge extension in middle of measuring plate VW 385/17.

• ‒ Set dial gauge (3 mm measuring range) to "0" with 2 mm preload.
• ‒ → Lift differential without turning; read off play on dial gauge and note it down.
• ‒ Measurement in following example: 0.50 mm

Note:

If the measurement has to be repeated, the differential must again first be turned 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.

• ‒ Define shim(s) as precisely as possible based on the table => Page 39-193.

Measuring frictional torque (check)

• ● Pinion shaft removed
• ● Differential fitted with shims "S1*" and "S2*"

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

Frictional torque specified values:

    1)    with at least 50 km service

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 special oil by the manufacturer.
• ◆ 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 .

Adjusting backlash

(Position of crown wheel in gearbox housing)

• ● Drive pinion with shim "S3" installed
• ● Differential with shims "S1*" + "S2*" installed

• ‒ Insert differential into final housing mount cover and tighten all bolts to 25 Nm.
• ‒ Turn differential 5 turns in both directions so that the taper roller bearings settle.

• ‒ → Fit measuring tools.
• ‒ Use dial gauge extension VW 382/10 (6 mm flat).
• ‒ Set measuring lever VW 388 to dimension "a" = 60 mm.
• ‒ 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 1 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 90° and repeat measurements a further 3 times.

Note:

If the individual measurements differ by more than 0.06 mm from each other, the installation of the crown wheel or the final drive set itself is not correct. Check installation; replace final drive set, if necessary.

Determining average backlash

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

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

• ● Drive pinion with shim "S3" installed
• ● Differential with shims "S1" + "S2" installed

• ‒ Turn 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.