Measuring backlash

WARNING: This page is about a different car, the 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Drive pinion and shims "S3*" and "S4*" installed

Installing differential with ring gear: S1* is installed on cover side, S2* in transmission housing.
Install final drive cover and tighten bolts to 25 Nm.
Turn differential 5 turns in both directions so that the tapered roller bearings settle.

Fig 1: Measuring Backlash

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Secure dial gauge holder VW 387 on housing.
Install dial gauge with dial gauge extension VW 382/10 (6 mm flat).
Set measuring lever VW 388 to dimension "a":

Dimension "a"	Ring gear diameter
67 mm	170 mm
72 mm	180 mm

Measure play between teeth flanks (backlash) as follows:
Turn ring gear until it makes contact with a tooth flank (end of backlash travel).
Set dial gauge to "0" with 2 mm pre-load.
Turn ring gear back until lying against an opposite tooth flank (backlash).

Read backlash and note value.
Turn ring gear 90 ° and repeat measurements another 3 times.

NOTE:

Fig 2: Installing Clamp 3177 "A"

Courtesy of VOLKSWAGEN UNITED STATES, INC.

If drive pinion rotates when the differential is turned, install bracket VW 3177 -A- so that backlash can be measured exactly.
Loosen the clamp in order to turn the ring gear.
Cut-out for large differential bevel gears must point toward drive pinion when differential is inserted.

With holder 3177 inserted, install differential offset by 180 ° and repeat measurement.