Ring/Pinion Adjustment

Explanation of Adjustment
Adjustment of the ring gear and pinion is important for quiet operation of the rear axle assembly. For this reason the pinion shaft and ring gear are already matched as a pair during production. They are checked on testing machines for correct contact pattern and low noise level in both directions of rotation. When the ring gear and pinion is tested, it is set according to the design dimension "R". Dimension "R" is the distance from the face of the pinion to the ring gear center line. The pinion is then moved in or out of mesh until the quietest operation is determined. The deviation from the design dimension (the in or out movement of the pinion) is called "r" and is etched on the face of the pinion. While making this test, the ring gear backlash is kept within a tolerance of 0.12 - 0.18 mm. The ring gear and pinion shaft is designed in such a way that the deviation "r" must always be added to the design dimension "R".

Earlier pinion assemblies had either a plus (+) or a minus (-) etched in front of the deviation "r" whereas on the newer pinion assemblies, the letter "N" precedes the deviation "r" on the pinion shaft.

Ring gear and pinion shaft sets are also stamped with a matching set number and should always be replaced as a complete set.





R - Design Distance (81.69 or 82.99mm)
r - Deviation from R, shown in 1/100 mm
1 - Deviation r
2 - Pair code
3 - Backlash

ADJUSTING DRIVE PINION
- Distance "F" is calculated by adding together design distance "P" and deviation "r" as indicated on face of drive pinion.
R= 81.69 mm for transmission type 930/32
R= 82.29 mm for transmission type 930/30/33/34




1 Deviation "Y" in 1/100 mm
2 Pair code

Examples:
Transmission type 930/32
The pinion face shows deviation "r" to be N 18
R = Design distance 81.69 mm
r = Deviation + 0.10 mm
_____________
E = Pinion setting = 81.87 mm

Transmission type 930/30/33/34
The pinion face shows deviation "r" to be N 12
R = Design distance 82.29 mm
r = Deviation + 0.12 mm
_____________
E = Pinion setting = 82.41 mm

- Install preassembled drive pinion and drive shaft without shims and torque clamping plate nuts to specifications.
- Install 4th gear with operating and guide sleeves, and place in 4th.






- Slide 48 x 4 x 148 mm piece of pipe onto drive pinion.
- Install thrust washer and cylindrical roller bearing.
- Mount gear housing and secure with two nuts.
- Install reverse gears I and III.
- Place appropriate pin or reverse gear shaft in bore of transmission case and slide in reverse gear II.
- Torque drive pinion nut to: 190-200 Nm (140-148 ft lb)
- Make sure that the taper roller bearing outer races fit tight in transmission case and side cover.





a = about 58 mm

- Set adjusting ring of universal gauge VW 385/1 to distance "a"
Slide centering discs 9109 on gauge. Screw in gauge plunger VW 385/14 with 30 mm dial gauge extention VW 385/56.
- Install taper roller bearing from differential, or spare taper roller bearing, on centering discs.





- Set master gauge VW 385/30 to pinion setting (82.41 mm in example) and place on master mandrel. Set dial gauge (3 mm range) at zero with 1 mm preload.
- Remove master gauge after setting dial gauge.





- Place gauge plate VW 385/17 on head of drive pinion.





- Place gauge mandrel in transmission case. The dial gauge extention is near the gauge plate.
- Install side transmission cover without seal and tighten the 4 nuts crosswise.

CAUTION: Do not use a hammer to set up the side transmission cover (this could cause the gauge plate, held by a magnet, to fall down). Position the cover by tightening the nuts evenly.





- Pull second centering disc so far out with the spindle that the gauge mandrel can just barely be turned by hand.
- Turn master mandrel carefully until dial gauge extension is vertical to face of drive pinion head. At this moment the dial gauge needle will reach its maximum point of deflection (inflection), so that it can be read.

NOTE: Measured value always deviates from set value in clockwise direction (small dial gauge needle between 1 and 2), i.e. in setting the dial gauge with 1 mm preload the value deviating from 1 must be added to shim thickness S.

Example:
If small dial gauge needle is between 1 and 2 and large needle points to 0,37 mm, with 1 mm dial gauge preload the shim thickness is 0.37 mm, whereby the thickness is always rounded off to the nearest 0,05 mm (e.g. 0.37 mm to 0.35 mm).

- Recheck distance "E" after installing shims. A deviation of 0.03 mm is permissible.

ADJUSTING RING GEAR
Determining total shim thickness "Stot" (S1 + S2)

NOTE: Drive pinion must be removed to determine preload of tapered roller bearing for differential.

- Make sure tapered roller bearing outer races fit tight in transmission case or side transmission cover.
- Install pertinent differential with one each 2.5 mmthick spacer on the ring gear end and opposite end,
- Insert differential in transmission case and turn several times.
- Install side transmission cover and tighten all nuts to: 22-25 Nm (16-18 ft lb)

NOTE: Unscrew one stud to mount dial gauge holder.

- Place gauge VW 385/17 on collar of differential.




A = Dial gauge extension30 mm long
B = Gauge plate VW 385/17

- Mount dial gauge holder VW 387 with dial gauge and extension on case and set dial gauge at zero with 2 mm preload.
- Move differential up and down, Read and note play on dial gauge.

NOTE: Do not turn differential while measuring play. since this would cause wrong readings.

Calculate "Stot"
"Stot" = shim thickness
+ measured value
+ tapered roller bearing preload

Example:
Shim thickness 5.O mm
Measured value 0.82 mm
Preload (constant value) 0.33 mm
_________
"Stot" = 6,15 mm

- Remove differential, pull off both tapered roller bearings and split up total shim thickness "Stot" as follows: Because of backlash adjustment later, spacer S1 is selected 0,20 mm thinner than spacer S2.

Example: Total thickness of spacers S1 + S2 = 15 mm.
Thickness of spacer S1: 6.15 mm divided by 2 equals 3.075 mm minus 0.20 mm which equals 2.875 mm.
Thickness of spacer S2: 6.15 mm divided by 2 equals 3.075 mm plus 0.20 mm which equals 3.275 mm.

NOTE: Spacers are available in thicknesses of 2.4 to 3.7 mm, in steps of 0.10 mm. A 0.25 mm thick shim permits spacing with 0.05 mm.

- Round off the spacer thicknesses to the available distance that the total shim thickness "S1" and "S2" is not changed.

Example:
Calculated spacer thicknesses
S1 + S2 = 2.875 = 3.275 = 6.15 mm

Rounded off spacer thicknesses
S1 + S2 = 2.87 = 3.27 = 6.15 mm

- Measure thickness of shims at several points with a micrometer. Max. permissible deviation 0.02 mm.
- Check shims for burrs and damage.

ADJUSTING BACKLASH
- Install pinion/ring gear set with shims "S3" used for pinion setting.

NOTE: Collar nut of drive pinion must be tightened to specified torque prior to measuring backlash.

- Install differential with tapered roller bearings and spacers (S1 + S2) in case.
Mount side transmission cover and tighten all nuts to: 22-25 Nm (16-18 ft lb).

NOTE: When tightening nuts, check frequently that there is still a certain amount of backlash. Never let the drive pinion start to clamp.

- Screw gauge lever VW 359 and adjuster VW 521/4 together and adjust lever length to 101 mm (measured from large hexagon surface to upper edge of ball) with gauge plunger 9196.
- Insert adjuster with clamping bush (special tool 9145) in differential and clamp tight.
- Turn differential in both directions several times to settle the tapered roller bearings.





Distance "a" 101 mm

- Mount dial gauge holder VW 357 with dial gauge and plain extension, so that dial gauge axis and lever are at right angles.
Turn ring gear carefully against stop and set dial gauge to zero. Turn back ring gear and read backlash. Note value.

NOTE: Hold drive pinion tight while measuring. This is done by clamping a suitable screwdriver between transmission case and reverse gear III.

- Repeat measurement three times turning ring gear 90° each time. Measured values must not deviate among each other by more than 0.05 mm.

NOTE: Backlash required is inscribed in ring gear.

- If specified backlash is not reached. change spacers (S1 and S2) again. However. do not change total shim thickness (Stot).