Audi Workshop Service and Repair Manuals

(Adjusting differential)

Repairs after which the crown wheel must be adjusted .

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

(Setting preload of taper roller bearing for differential)

• ● Drive pinion removed

• ‒ Remove seal and outer races of both taper roller bearings for differential.
• ‒ Remove shims => Page 39-10.
• ‒ → Drive outer race for taper roller bearing with shim "S2" into gearbox housing. For measurement purposes an "S2*" shim 1.20 mm thick (2 shims of 0.60 mm) is used.

Note:

For measurement purposes a shim "S2" of 1.20 mm is initially inserted which is designated "S2*" in the following. After determining backlash, "S2*" will be replaced by the correct shim "S2".

• ‒ → Press outer race for taper roller bearing without shim "S1" into cover for differential.
• ‒ 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 cover for differential.
• ‒ Install cover for differential with 4 bolts (25 Nm).
• ‒ Position gearbox so that the cover for differential faces up.

• ‒ Turn differential 5 turns in both directions so that the taper roller bearings settle.
• ‒ → Set up measuring tool with 30 mm dial gauge extension -A-.
• ‒ Set dial gauge (3 mm measuring range) to "0" with 2 mm preload

Note:

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

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

• ● Measurement in following example: 0.62 mm.

Notes:

• ◆ → Secure special tools VW 521/4 and VW 521/8 on right of differential (gearbox side) to lift differential.
• ◆ If the measurement has to be repeated, the differential must again 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 unchanged.

Measuring friction torque (check)

Notes:

• ◆ Differential tapered roller bearings are low friction bearings. Therefore the friction 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 friction torque measurement. The bearings have already been treated with a special oil by the manufacturer.

• ● Drive pinion removed

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

•     B -    Socket

• ‒ Read off friction torque.

Friction torque specifications:

Note:

If the final drive set (drive pinion and crown wheel) is being adjusted, perform the adjustment of the drive pinion now and check the adjustment .

Measuring backlash

(Position of crown wheel in gearbox housing)

• ● Drive pinion with shims "S3" and "S4" installed

• ‒ Install differential.

• ‒ Turn the differential 5 turns in each direction to settle the taper roller bearings.
• ‒ → Secure dial gauge retainer VW 387 onto housing.
• ‒ Insert adjustment device VW 521/4 and VW 521/8 for crown wheel.
• ‒ Fit dial gauge with dial gauge extension VW 382/10 (6 mm flat).
• ‒ Set measuring lever VW 388 to dimension a = 79 mm.
• ‒ Determine play between the teeth flanks as follows:
• ‒ Turn crown wheel until it makes contact with a tooth flank (end of backlash travel).
• ‒ Set dial gauge to "0" with 2 mm preload.
• ‒ 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

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

• ● Result: The average backlash is 1.96 /4 = 0.49 mm

Determining thickness of shim"S2"

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

=> Parts catalogue

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) from table. Part numbers

=> Parts catalogue

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.

→ Performing check measurement

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

Notes:

• ◆ If the backlash lies outside the tolerances, the adjustments must be repeated. But the total shim thickness "Stotal" must remain the same.
• ◆ The individual measurements must not differ by more than 0.06 mm from each other.