Audi Workshop Service and Repair Manuals

Adjusting crown wheel (Adjusting differential)   Note The crown wheel only needs to be re-adjusted according to the following instructions if the gearbox housing, cover for final drive, tapered roller bearings for differential, differential cage or final drive gear set are being renewed. Table of adjustments → Chapter

Special tools and workshop equipment required

t	End measuring plate -VW 385/17-

t	Universal dial gauge bracket -VW 387-

t	Measuring lever -VW 388-

t	Crown wheel adjusting tool -VW 521-

t	Retainer -3177-

t	Torque wrench -V.A.G 1331-

t	Dial gauge extension -VW 382/10-

t	Thrust plate -VW 402-

t	Press tool -VW 408 A-

t	Removal and installing tool -VW 459/2-

t	Press tool -VW 472/1-

t	Extractor lever -VW 681-

t  Thrust piece -2050- Determining total shim thickness “Stotal” for shims “S1” plus “S2” (Adjustment of pre-load of tapered roller bearings for differential) l  Pinion shaft removed. –  Pull out flange shaft oil seals using oil seal extractor -VW 681-. –  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 1.22 mm thick “S2*” shim (or 2 shims of 0.61 mm).   Note For measurement purposes a 1.22 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. –  Insert differential without drive wheel for speedometer sender -G22- into gearbox housing. The crown wheel is located on the left side (cover side). –  Fit cover for final drive and tighten 4 bolts to 25 Nm in diagonal sequence. –  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 with 30 mm dial gauge extension -A-. –  Set dial gauge (3 mm measuring range) to “0” with 2 mm preload. l  Tip of dial gauge must be located at centre of differential. –  Raise differential without turning, read play off dial gauge and note down (example: 0.62 mm).   Note

t  Secure crown wheel adjusting tool -VW 521/4- and -VW 521/8- on right of differential (housing side) to lift differential. 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:

Example:
	Inserted shim(s) “S2*”	1.22 mm
+	Measured value	0.62 mm
+	Bearing preload (constant value)	0.25 mm
=	Total shim thickness “Stotal” for “S1” plus “S2”	2.09 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” + “S2”	2.09 mm
–	Inserted shim(s) “S2*”	1.22 mm
=	Thickness of shim “S1*”	0.87 mm

Select correct shims from → Electronic parts catalogue. Measuring backlash (Position of crown wheel in gearbox housing) l  Pinion shaft fitted with shims “S3” and “S4”. –  Install differential with shims “S1*” and “S2*”. –  Fit cover for final drive and tighten bolts to 25 Nm. –  Turn differential 5 turns in both directions so that the tapered roller bearings seat properly.

–  Secure dial gauge bracket -VW 387- to housing. –  Fit dial gauge with dial gauge extension -VW 382/10- (6 mm flat). –  Set measuring lever -VW 388- to dimension “a” according to crown wheel Ø:

Distance “a”	Crown wheel Ø
67 mm	170 mm
72 mm	180 mm

–  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 another 3 times.   Note

t  If the pinion shaft rotates when the differential is turned, fit retainer -3177--A- so that the backlash can be measured exactly. t  Loosen the clamp in order to turn the crown wheel. t  When inserting the differential, the opening for the differential bevel gears must then face the pinion shaft. –  If the retainer -3177- has been fitted, install differential turned through 180° and repeat measuring procedure. 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 from each other by more than 0.06 mm, the installation of the crown wheel or the final drive gear set itself is not correct. Check installation; renew final drive gear set if necessary. Determining thickness of shim “S2”    Formula: “S2” = “S2*” – backlash + lift

Example:
	Inserted shim(s) “S2*”	1.22 mm
–	Average backlash	0.29 mm
+	Lift (desired average value for backlash)	0.15 mm
=	Thickness of shim “S2”	1.08 mm

–  Select thickness of required shim(s) from following table:

Available shims - Thickness of shims in mm 1)2)
0.45	0.61	0.77
0.49	0.65	0.81
0.53	0.69	0.85
0.57	0.73
l  1) For Part Nos. refer to → Electronic parts catalogue. l  2) 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”	2.09 mm
–	Thickness of shim “S2”	1.08 mm
=	Thickness of shim “S1”	1.01 mm

–  Select thickness of required shim(s) from following table:

Available shims - Thickness of shims in mm 1)2)
0.45	0.61	0.77
0.49	0.65	0.81
0.53	0.69	0.85
0.57	0.73
l  1) For Part Nos. refer to → Electronic parts catalogue. l  2) 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. l  Specification: 0.12 ... 0.22 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.