Head Bevel Gear, Adjusting

Head bevel gear, adjusting





Special tools, testers and auxiliary items required
^ Transmission support VW 353
^ Magnetic plate VW 385/17
^ Universal Dial Gauge Holder VW 387
^ Measuring Lever, Adjustable VW 388
^ Ring gear adjustment device VW 521
^ Dial gauge

A new head bevel gear adjustment is necessary if:
^ Rear axle housing
^ Tapered roller bearing for head bevel gear/input shaft
^ Cover or the
^ Gear set
are replaced.

Preload of tapered roller bearing for differential, setting
Shaft bevel gear is removed.
- Insert 1.0 mm adjustment shim into seat of outer race for the small tapered roller bearing (S 2 side).

For initial measurement, an adjustment shim S 2 with a thickness of 1.00 mm is inserted. It is designated as S 2 in the following. After determining backlash, S 2 is replaced by final adjustment shim S 2.

- Press in outer race.
- Insert head bevel gear/input shaft with tapered roller bearing.
- Assemble cover with outer race for large tapered roller bearing without O-ring, without flanged shaft seal and without adjustment shim S 1.





- Install dial gauge and set to "0" with 2 mm pre-load.
- Move head bevel gear/input shaft up and down (in direction of - arrow -)
- Check play on dial gauge and determine S total

Example:
"S total " = S 2 + measurement result + preload





Determining thickness of adjustment shim S 1

Note:
^ Initial shim S 1 is replaced with final shim S 1 after backlash has been determined.
^ The total shim thickness "S total remains unchanged.

S 1 = S total - S 2

Example:





Torsional backlash, measuring
Drive pinion housing with shaft bevel gear and S 3 installed

Install head bevel gear / input shaft: S 1 is on cover side, S 2 installed in rear axle housing.





- Install measuring tools.
^ Dimension "a" = 43.5 mm
^ Install Measuring Lever VW 388 so that dial gauge extension is at a right angle to measuring surface

- Twist head bevel gear/input shaft until stop. Set dial gauge to zero, turn back head bevel gear/input shaft and read off backlash. Note value.
- Loosen clamping screw of roll pin and repeat three more times after turning head bevel gear/input shaft an additional 90°. Add the four results and calculate the average backlash.

Calculating mean backlash

Example:





Average backlash: 1.20 mm : 4 = 0.30 mm.

Determining shim thickness S 2





Lift = 0.20 mm

Example:





Available adjustment shims for S 2





- Install determined adjustment shim S 2 in place of S 2.

2 shims corresponding to measured value may be installed.

- Varying tolerances make it possible to measure required shim thickness exactly.
- Press in outer race again and insert head bevel gear/input shaft.

Determining shim thickness S 1





Available adjustment shims for S 1





- Install determined shim S 1.

2 shims corresponding to measured value may be installed.

- Different tolerances make it possible to measure the required shim size exactly.
- Press in outer race again.
- Install cover.

Performing control measurement - measuring backlash
- It must be 0.12 - 0.20 mm.