audi Workshop Repair Guides

Audi Workshop Service and Repair Manuals

ABOUT US
Determining thickness of shim "S4” when renewing output flange > < Dismantling and assembling bevel box

A3 Mk1

Adjusting bevel box
Adjusting bevel box
Adjusting shaft bevel gear and bevel gear (final drive gear set)
t  Careful adjustment of the shaft bevel gear and bevel gear is essential to ensure that the final drive gear set gives long service and runs silently. During manufacture the bevel gear and shaft bevel gear are therefore matched and checked on testing machines to ensure correct mesh pattern and silent running. The position for quietest running is obtained by moving the shaft bevel gear axially and, at the same time, maintaining the backlash within the specified tolerance.
t  The deviation “r” from the master gauge “Ro” is marked on the bevel gear. If required, the shaft bevel gear and bevel gear (final drive gear set) must always be renewed together.
   
Adjustment and marking of final drive gear set
A - Bevel gear
B - Shaft bevel gear
1 - Gear set pairing number “8033”.
2 - Tolerance of shaft bevel gear “D = 3”
q   Value for adjustment in production
3 - Backlash “Sd = 0.20”
q   Specification when checking adjustment
4 - Deviation (tolerance) “r” is based on the master gauge used on the test machine in production. Deviation “r” is always stated in 1/100 mm. For example: “38” indicates r = 0.38 mm
Ro - Length of master gauge used on test machine “Ro” = 36.20 mm
R - Actual distance between bevel gear axis and face of shaft bevel gear in position of quietest running for this gear set.

   
Position of shims
S1 - Shim for friction torque of bevel gear tapered roller bearing
S2 - Shim for friction torque and positioning of bevel gear
S3 - Shim for shaft bevel gear
S4 - Shim for friction torque of shaft bevel gear tapered roller bearing

Adjustment overview (bevel box)
  Note
If repairs have been carried out on the bevel box it is only necessary to adjust the shaft bevel gear, bevel gear or the complete final drive gear set when parts are renewed which directly influence the adjustment of the final drive. Refer to the following table to avoid unnecessary adjustment work:
   
Components renewed:Components requiring adjustment:
 Shaft bevel gear
“S3”+“S4” via deviation “r” → Chapter		Bevel gear
“S1”+“S2” → Chapter
Final drive housingx 1)x
Cover x 2)
Final drive gear set (shaft bevel gear and bevel gear with input shaft)xx
Tapered roller bearings for shaft bevel gearx 
Tapered roller bearings for bevel gear x
Pinion housingx 
Output flangex 3) 
l  1)“S3” only → Anchor. The shaft bevel gear is removed together with the pinion housing. Therefore the shim “S4” remains in place and is unchanged.
l  2)“S1” only (via previously measured total friction torque).
l  3)“S4” only (calculated from difference between measurements → Chapter).

Re-adjustment sequence for final drive gear set
To avoid unnecessary work, keep to the following sequence when adjusting the shaft bevel gear and bevel gear.
1.  Adjust shaft bevel gear “S3”+“S4”.
–  Determine thickness of shim “S4” and install shim. This sets the preload of the tapered roller bearings for the shaft bevel gear.
–  Determine thickness of shim “S3” and install shim. The shaft bevel gear is thus fixed axially such that the distance from the centre of the bevel gear to the face of the shaft bevel gear corresponds to the locating distance “R” calculated during production.
–  Check adjustment of “S3”.
2.  Adjust bevel gear “S1”+“S2”.
–  Adjust preload of tapered roller bearings for bevel gear via “Stotal” and friction torque.
–  Adjust backlash. Select shims “S1” and “S” so that the required backlash between shaft bevel gear and bevel gear is obtained.
–  Check backlash.
The object of the adjustment is to reproduce the setting for quietest possible running, as obtained on the test machine in production. For good results, maximum care and cleanliness are very important when performing repairs and taking measurements.
   

Determining thickness of shim "S4” when renewing output flange > < Dismantling and assembling bevel box