1998 AUDI A4 01W Transmission Pinion Shaft Ring Gear Adjustment Workshop Manual

39-55

- Lift differential without turning it, read play on
dial indicator and note.
Dimension in the following example: 0.62 mm

Notes:

To lift differential, secure VW521/4 locking sleeve and VW521/8
bushing (for transmissions without polygon bearing) or VW521/12 (for
transmissions with polygon bearing) to right side of differential
(housing side). If measurement has to be repeated, turn differential again 5 rotations
in both directions to seat tapered roller bearing.
Formula:
"Stotal"
=
"S2*" + measured value + bearing preload
Example:

Installed shim "S2*" 1.20 mm
+ Dimension 0.62 mm
+ Bearing preload (constant) 0.30 mm
=
Total shim thickness "Stotal" for "S1 + S2"
2.12 mm
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39-56

Determining thickness of shim "S1*"

Notes:

"S1*" is used for the initial measurement. After
determining backlash, "S1*" is replaced with
final shim "S1."
The total shim thickness "Stotal" remains
unchanged.

Formula:
"S1*"
=
"Stotal" - "S2*"

Example:


Total shim thickness "Stotal" for "S1"
+ "S2"
2.12
mm
- Installed shim "S2*" 1.20
mm
= Thickness of shim "S1*" 0.92
mm
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39-57

Measuring friction torque (check
measurement)

Notes:

Tapered roller bearings for differential are low-
friction. Measurement of friction torque only has
a limited use as a check. Correct adjustment is
only possible by determining the total shim
thickness "Stotal."
Do not lubricate new tapered roller bearings for
measuring friction torque. The bearings have
already been treated by a special oil by the
manufacturer.
Pinion shaft removed

Friction torque specified values:
Note: - Install torque gauge 0-600 Ncm -A- on differential.
- Read friction torque.New bearings
Used bearings
200 - 350 Ncm 30 - 60 Ncm
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For a readjustment of the gear set, the pinion shaft adjustment should
now be checked Page 39
-35
.
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39-58

Measuring backlash
(Position of ring gear in transmission housing)

Pinion shaft with shims "S3*" and "S4*"
installed

- Install differential.

- Turn differential 5 rotations in each direction to
seat tapered roller bearing.

- Secure VW387 dial gauge holder on housing.
- Install VW521/4 locking sleeve and VW521/8 bushing (for
transmissions without polygon bearing) or VW521/12 (for transmissions
with polygon bearings).
- Install dial indicator with VW382/10 extension pin, 6 mm.
- Set VW388 measuring lever to dimension "a:"Dimension "a"
Ring gear diameter
67 mm 170 mm
72 mm 180 mm
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39-59

- Determine play between teeth flanks as
follows:

- Turn ring gear until it contacts a tooth flank
(end of backlash travel).

- Set dial indicator to 0 with 2 mm preload.

- Turn ring gear back until it contacts opposite
tooth flank (backlash).

- Read backlash and note.

-
Turn ring gear another 90 and repeat
measurement 3 times.
Notes:

If pinion shaft turns when turning differential, install 3177 clamp -A- so
that an exact backlash measurement can be made. Loosen clamping piece to turn the ring gear further.Differential must be installed with cutout for differential bevel gears
facing pinion shaft.
-
If 3177 clamp is installed, install differential 180 to final position and
repeat measurements.
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39-60

Determining average backlash

- Add four measured values together and divide
total by 4 to determine average.

Example:

1st Measurement 0.28 mm
+ 2nd Measurement 0.30 mm
+ 3rd Measurement 0.30 mm
+ 4th Measurement 0.28 mm
= Total of measurements 1.16 mm

Result: the average backlash is 1.16 mm 4
= 0.29 mm

Note:
If the measured values differ more than 0.06 mm
from each other, the installation of ring gear or
gear set itself may not be correct. Check
installation and replace gear set if necessary.
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39-61

Determining thickness of shim "S2"

Formula:
"S2"
=
"S2*" - backlash + lift

Example:

Installed shim "S2*" 1.20 mm
- Average backlash 0.29 mm
+ Lift (constant) 0.15 mm
= Thickness of shim "S2" 1.06 mm

- Determine shim(s) according to table. Part
numbers parts catalog
Available shims for "S2"

Shim thickness (mm) 1)
0.45 0.65 0.85
0.50 0.70 0.90
0.55 0.75
0.60 0.80

1) Using shim tolerances it is possible to find the
exact shim thickness required; insert two shims if
necessary.
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