Determining total shim thickness Stot

The ring gear must be readjusted if the transmission case, transmission side cover, taper roller bearing for differential, differential housing or drive set have been replaced.

The drive pinion must be removed in order to determine the preload of the differential

1. Remove adjusting shim "Sr (in trans-

2. Adjusting shim "S2" remains in the trans-

3. Make sure that the bearing outer races of the tapered roller bearings are well seated in the transmission case or in the trans-

4. Insert differential into transmission case and

5. Fit transmission side cover without seals and tighten all hexagon head bolts to

6. Place gauge block plate 9281 on the collar

7. Fasten universal dial gauge holder VW 387 with dial gauge and extension to the case and set to 0 with 2 mm preload.


A - Dial gauge extension (approx. 30 mm long) B - Gauge block plate 9281

8. Using a suitable tool, move differential up Read off backlash on the dial gauge and

Do not turn differential while measuring backlash as this will give an incorrect reading.

9. Remove adjusting shim "S2" and determine thickness using a micrometer.

"Stot." = Thickness of adjusting shim "S2" + pressure fit of taper roller bearings

Thickness of adj. shim "S2"

Measured value

Press fit (constant value)

Thickness of adj. shim "S2"

Measured value

Press fit (constant value)

11. Spread calculated shim thickness "Stot" as

To start with the backlash adjustment, the thickness of adjusting shim "Sr is reduced by 0.40 mm while the thickness of adjusting shim "S2" is increased by 0.40 mm.

Total shim thickness of adjusting shims Si + S2 = 2.85 mm Thickness of adjusting shim "Sr 2.85 mm

Thickness of adjusting shim "S2" 2.85 mm =

The adjusting shims are avail, in thickneses of 1.0...2.0 mm in increments of 0.05 mm.

The shim tichknesses calculated must be rounded up or down for plausible dimensions that will not alter the total shim thickness Si

Calculated shim thickness

Rounded down shim thickness

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  • Lachlan
    How to determine differential shim size in porsche 928?
    5 months ago

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