Audi A4 Workshop Service and Auto Repair Manuals

(differential adjustment)

Operations following which crown wheel has to be adjusted => Table, Page 39-57

Special tools, workshop equipment, testers, measuring instruments and other items required

• ◆ Mandrel VW 295
• ◆ Measuring device VW 382
• ◆ Universal measuring tool VW 385
• ◆ Universal dial gauge holder VW 387
• ◆ Test lever VW 388
• ◆ Thrust plate VW 402

• ◆ Pressing-out and pressing-in tool VW 459
• ◆ Adjustment tool for crown wheel VW 521
• ◆ Thrust plate 30-205
• ◆ Fitting mandrel 30-505
• ◆ Thrust pad 3062
• ◆ Torque gauge 0 ... 600 Ncm
• ◆ Dial gauge
• ◆ Dial gauge extension

Determining total thickness "Stot" for shims "S1" + "S2"

(adjustment of pre-load of taper roller bearings for differential)

• ● Drive pinion removed

• ‒ Remove oil seal and outer races of both differential taper roller bearings.
• ‒ Take out shims .
• ‒ → Drive outer race for taper roller bearing with shim "S2" into gearbox housing. Use is made for measurement of a shim "S2*" of thickness 1.20 mm (2 x 0.60 mm thick shims).

Note:

A 1.20 mm thick shim "S2" is provisionally inserted as standard measure. This is referred to in the following as "S2*". "S2*" is replaced with final "S2" after determining backlash.

• ‒ → Press outer race for taper roller bearing without shim "S1" into cover for differential.
• ‒ Insert differential without drive wheel for speedometer sender -G22 in gearbox housing. Crown wheel is located on left side in front of cover for differential.
• ‒ Fit differential cover with 4 bolts (25 Nm).
• ‒ Position gearbox such that differential cover faces upwards.

• ‒ Give differential 5 turns in each direction so that taper roller bearing settles.
• ‒ → Attach measuring tool, making use of 30 mm dial gauge extension.
• ‒ Set dial gauge (3 mm measuring range) -A- to "0" with 2 mm pre-load.

Note:

Tip of dial gauge must be located at centre of differential.

• ‒ Raise differential without turning, read clearance off dial gauge and note down.

• ● Measured value in the following example: 0.62 mm

Notes:

• ◆ → To lift differential, attach special tools VW 521/4 and VW 521/8 to right of differential (housing end).
• ◆ If measurement is to be repeated, differential must first be turned again5 times in each direction to allow taper roller bearing to settle.

Determining thickness of shim "S1*"

Notes:

• ◆ Provisional shim "S1*" is replaced by ultimate shim "S1" after determining backlash.
• ◆ The total shim thickness "Stot" remains unchanged.

Measuring friction torque (check)

Notes:

• ◆ Taper roller bearings for differential are of low-friction design. Friction torque can therefore only be used to a limited extent for check purposes. Correct setting is only possible by means of determining total shim thickness "Stot"
• ◆ Do not additionally lubricate new taper roller bearings for friction torque measurement. Bearings are treated at the factory with a special oil.

• ● Drive pinion removed

• ‒ → Apply torque gauge 0 ... 600 Ncm -A- at differential.

•     B -    Socket attachment

• ‒ Take friction torque reading.

Friction torque specifications:

Note:

In the event of re-adjustment of pinion set, drive pinion is now to be adjusted and checked .

Measuring backlash

(position of crown wheel in gearbox housing)

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

• ‒ Install differential.

• ‒ Give differential 5 turns in both directions so that taper roller bearings settle.
• ‒ → Attach dial gauge holder VW 387 to housing.
• ‒ Insert adjustment tool for crown wheel VW 521/4 and VW 521/8.
• ‒ Insert dial gauge with extension VW 382/10 (6 mm flat).
• ‒ Set test lever VW 388 to dimension "a" = 79 mm.
• ‒ Determine backlash between tooth flanks as follows:
• ‒ Turn crown wheel until it makes contact with tooth flank (backlash end).
• ‒ Set dial gauge to "0" with 2 mm pre-load.
• ‒ Turn back crown wheel until it makes contact with opposite tooth flank (backlash).

• ‒ Take backlash reading and note down measured value.
• ‒ Turn crown wheel by a further 90° in each case and repeat measurement 3 times.

Note:

If the individual values determined in this measurement differ by more than 0.06 mm, there is a problem either with the installation of the crown wheel or with the actual pinion set. Check assembly operations and replace pinion set if necessary.

Determining average backlash

• ‒ Add the 4 measured values together and divide the total by 4.

• ● Result: Average backlash = 1.96 mm : 4 = 0.49 mm

Determining thickness of shim "S2"

• ‒ Determine shim(s) as per table. Part numbers

=> Parts List

Shims available for "S2"

    1)    The tolerances of the shims permit determination of any thickness; fit 2 shims if necessary

Determining thickness of shim "S1"

• ‒ Determine shim(s) as per table. Part numbers

=> Parts List

Shims available for "S1"

    1)    The tolerances of the shims permit determination of any thickness; fit 2 shims if necessary

→ Check measurement

• ‒ After fitting shims "S1" and "S2", give differential 5 turns in both directions so that taper roller bearings settle.
• ‒ Measure backlash 4 times on periphery.
• ‒ Specification: 0.12 ... 0.22 mm

Notes:

• ◆ Adjustment must be repeated if backlash is outside tolerance. The total shim thickness "Stot" must not be changed.
• ◆ Deviation between individual measured values must not exceed 0.06 mm.