Audi Workshop Service and Repair Manuals

Adjusting crown wheel

(Adjusting differential)

Special tools and workshop equipment required

t	Drift -VW 295-

t	Dial gauge extension -VW 382/10-

t	End measuring plate -VW 385/17-

t	Universal dial gauge bracket -VW 387-

t	Adjustable measuring lever -VW 388-

t	Thrust plate -VW 402-

t	Press tool -VW 408 A-

t	Crown wheel adjusting tool -VW 521-

t	Tube -30 - 14-

t	Thrust piece -2050-

t	Thrust plate -3005-

t	Torque wrench -V.A.G 1331-

t	Dial gauge

t	Dial gauge extension, 30 mm

It is necessary to readjust the crown wheel when the following components have been renewed: Gearbox housing, cover for final drive, tapered roller bearings for differential, differential cage or final drive gear set Table of adjustments → Chapter Determining total shim thickness “Stotal” for shims “S1” plus “S2” (Setting preload of tapered roller bearings for differential) l  Pinion shaft removed –  Remove flange shaft oil seals. –  Remove tapered roller bearing outer races for differential and take out shims → Chapter.

–  Drive outer race for tapered roller bearing (right-side) with shim “S2” into gearbox housing. For measurement purposes use a 1.30 mm thick “S2*” shim (or 2 shims of 0.65 mm).   Note For measurement purposes a 1.30 mm thick shim “S2” is inserted provisionally. This is referred to in the following as “S2*”. “S2*” is exchanged with the final shim “S2” after determining backlash.

–  Press outer race for tapered roller bearing (left-side) without shim “S1” into cover for final drive. –  Install differential in gearbox housing. The crown wheel is positioned on the left-hand side (same side as cover for final drive). –  Fit cover for final drive with 4 bolts (20 Nm). –  Turn gearbox so that cover for final drive points upwards. –  Turn differential 5 turns in both directions so that the tapered roller bearings settle. –  Place measuring plate -VW 385/17- on differential.

–  Set up measuring tool using 30 mm extension. –  Set dial gauge (3 mm measuring range) -A- to “0” with 2 mm preload.   Note The tip of the dial gauge must be applied to the centre of the differential. –  Raise differential without turning, read clearance off dial gauge and note down. l  Measurement in following example: 0.62 mm   Note

t  To lift differential, secure crown wheel adjusting tool -VW 521/4- and -VW 521/12- on right side of differential (housing side). t  If the measurement has to be repeated, the differential must again first be turned 5 turns in each direction to settle the tapered roller bearings. Formula: “Stotal” = “S2*” + measured value + bearing preload

Example:
	Inserted shim(s) “S2*”	1.30 mm
+	Measured value	0.62 mm
+	Bearing preload (constant value)	0.25 mm
=	Total shim thickness “Stotal” for “S1” plus “S2”	2.17 mm

Determining thickness of shim “S1*”   Note t  Provisional shim “S1*” is replaced with final shim “S1” after determining backlash. t  Total shim thickness “Stotal” remains unchanged. Formula: “S1*” = “Stotal” – “S2*”

Example:
	Total shim thickness “Stotal” for “S1” plus “S2”	2.17 mm
–	Inserted shim(s) “S2*”	1.30 mm
=	Thickness of shim “S1*”	0.87 mm

Select correct shims from → Electronic parts catalogue. Measuring backlash l  Pinion shaft fitted with shims “S3” and “S4”. –  Install differential with crown wheel: S1 is fitted on cover side, S2 in gearbox housing. –  Fit cover for final drive and tighten bolts to 20 Nm. –  Insert crown wheel adjusting tool -VW 521/4- and -VW 521/12-. –  Turn differential 5 turns in both directions to settle tapered roller bearings.

–  Secure universal dial gauge bracket -VW 387- to housing. –  Fit dial gauge with dial gauge extension -VW 382/10- (6 mm flat). –  Adjust measuring lever -VW 388- to distance “a” = 79 mm (for Ø 188 mm crown wheel). Measure play between teeth faces (backlash) as follows: –  Turn crown wheel until it makes contact with the face of one tooth (end of backlash travel). –  Preload dial gauge to 2 mm and set to “0”. –  Turn back crown wheel until it makes contact with opposite tooth face (backlash). –  Take backlash reading and note down measured value. –  Turn crown wheel through 90° and repeat measurements a further 3 times.   Note

If the pinion shaft turns when taking the measurement, it can be locked by engaging 2 gears at the same time, (e.g. reverse gear -arrow A- and 1st gear -arrow B-. Determining average backlash –  Add the four measured values together and divide by four.

Example:
	1st measured value	0.28 mm
+	2nd measured value	0.30 mm
+	3rd measured value	0.30 mm
+	4th measured value	0.28 mm
=	Sum of measured values	1.16 mm

l  Result: the average backlash is 1.16 mm : 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 gear set itself is defective. Check installation; renew final drive gear set if necessary. Determining thickness of shim “S2” Formula: “S2” = “S2*” - measured backlash + specified backlash

Example:
	Inserted shim “S2*”	1.30 mm
–	Measured average backlash	0.29 mm
+	Specified backlash (desired average value for backlash)	0.20 mm
=	Thickness of shim “S2”	1.21 mm

–  Determine shim(s) according to table. For part number, refer to → Electronic parts catalogue. Available shims for “S2”

Shim thickness (mm) 1)
0.45	0.61	0.77
0.49	0.65	0.81
0.53	0.69	0.85
0.57	0.73
1) The exact shim thickness required can be obtained by using the shim tolerance variations. Install two shims if necessary.

Determining thickness of shim “S1” Formula: “S1” = “Stotal” – “S2”

Example:
	Total shim thickness “Stotal” for “S1” plus “S2”	2.17 mm
–	Thickness of shim “S2”	1.21 mm
=	Thickness of shim “S1”	0.96 mm

–  Determine shim(s) according to table. For part number, refer to → Electronic parts catalogue. Available shims for “S1”

Shim thickness (mm) 1)
0.45	0.61	0.77
0.49	0.65	0.81
0.53	0.69	0.85
0.57	0.73
1) The exact shim thickness required can be obtained by using the shim tolerance variations. Install two shims if necessary.

Checking adjustment –  After installing shims “S1” and “S2”, turn differential 5 turns in both directions so that the tapered roller bearings settle. –  Measure backlash four times on circumference. t  Specification: 0.12 ... 0.28 mm   Note t  Adjustment must be repeated if backlash is outside tolerance. The total shim thickness “Stotal” must remain unchanged. t  The discrepancy between individual measured values must not exceed 0.06 mm.