Adjusting Drive Set
Practical Procedure When Readjusting The Drive Set- If it is necessary to adjust drive pinion and ring gear, following this sequence will ensure an efficient working procedure:
1. Determine the total thickness of shims "Stot (S1 plus S2). For the specified pretension on tapered roller bearing/differential.
2. Determine the thickness of shim "S".
3. Split the total thickness "Stot" into S1 and S2 so that the specified circumferential backlash is given between ring gear and drive pinion.
- The purpose of this adjustment is to restore the smoothest running position which can be achieved on test equipment in the production line.
- Greatest possible cleanliness when performing all assembly work and measuring procedures are prerequisites for a correct result.
When carrying out assembly work on the final drive assembly, it is only necessary to readjust drive pinion and ring gear or drive set if components have been replaced which have a direct influence on the adjustment. Refer to the above table to avoid unnecessary adjustment work.
Adjusting Drive Set
1 - Shim S1
2 - Shim S2
3 - Shim S3
E - Adjustment dimension
NOTE: Correct results may only be achieved if assembly work and measuring procedures are carried out conscientiously observing cleanliness. The setting of drive pinion and ring gear is a determining factor for the service life and smooth running of the rear-axle drive. Drive pinions and ring gears were therefore matched during production which have been checked for good surface appearance and low noise in both directions of rotation on special test equipment. The position at which smoothest running can be achieved is determined by shifting the drive pinion axially, whereby the ring gear is kept within the tolerance of the prescribed tooth-flank backlash. Deviation "r" from the specified design dimension "Ro" is measured, added to design dimension "Ro" and embossed on the ring gear as setting value "E".
Ro = Design dimension
r = Deviation r
1 = Adjustment dimension (Ro + r), e.g. E 60.95
2 = Flank backlash, e.g. F 0.16
3 = Matching number
1 = Setting dimension "E"
NOTE: The setting dimension "E" is given on the ring gear.
- Install complete gear set without "S3" shims and tighten all hexagon nuts for tensioning plate to: 23 Nm (17 ft lb).
a = approx. 65 mm
- Set adjusting ring of measuring mandrel VW 385/1 to dimension "a".
- Assemble measuring mandrel with centering disk 9109, tapered-roller bearings, plunger VW 385/14 and dial-gauge extension VW 385/15.
- Set measuring mandrel with adjuster 385/30 to adjusting dimension (60.95 mm in the example). Set dial gauge (3 mm measuring range) to 0 with 1 mm pretension.
- Block input shaft with Special Tool 9253, select 4th gear and screw Special Tool 9283 onto hollow shaft hand tight.
- Apply final dimension plate 9281 to drive pinion head and insert measuring mandrel into transmission case. Dial-gauge extension located in the area of the final dimension plate.
- Fit side transmission cover without 0-ring and fasten cross-wise with 4 nuts.
NOTE: Do not use a hammer when fitting the side transmission cover (the magnet- fitted final dimension plate may fall). Settle cover in installation position by tightening the nuts uniformly.
- Pull second centering disk with spindle towards the outside until the measuring mandrel can still just be turned by hand.
- Turn measuring mandrel carefully until the dial-gauge extension is vertical to the facing edge of the drive-pinion head. At this point, the pointer of the dial gauge reaches maximum deflection (reverse point), and the dial gauge must be read.
NOTE: The measured value always deviates from the set dimension clockwise (the smaller pointer on the dial gauge is between 1 and 2), i.e. if the dial gauge is set with 1 mm preload, the value deviating from 1 is taken as shim thickness "S3".
Example
If the small pointer on the dial gauge indicates between 1 and 2 and the large pointer indicates 0.37 mm, then take 0.37 mm as being the shim thickness (with 1 mm gauge preload). Always round up or down to the nearest 0.05 mm. (e.g. 0.37 mm to 0.35 mm).
- After providing the necessary shims, check setting value "E" again. A deviation ± 0.03 mm is permissible.
Adjusting Ring Gear
NOTE: The ring gear must be adjusted if the transmission case, side transmission cover, tapered-roller bearing for differential, differential housing or drive set have been replaced. The drive pinion must be removed to determine the preload of tapered-roller bearing on the differential.
- Determine total shim thickness "S tot" (S1 + S2).
- Make sure that the outer bearing races of the tapered roller bearings are well seated in the transmission case or side transmission cover.
- Fit one spacer ring, 2.5 mm thick, on the ring gear side and opposite side of the differential to be used.
- Insert differential into transmission case and crank several times.
- Fit side transmission cover without seal and tighten all hexagon nuts with 23 Nm (17 ft.lb.).
- Lay final dimension plate VW 385/17 on the collar of the differential.
A = Dial-gauge extension (approx. 30.. .40 mm long)
B = Final dimension plate "N" 385/17
- Fasten universal dial-gauge holder VW 387 with dial gauge and extension to the case and set to 0 with 2 mm preload.
- Move differential up and down. Read off backlash on the dial gauge and note.
NOTE: Do not turn differential while measuring backlash as this will falsify the measuring result.
- Calculate "S tot"
"S tot"= Fitted shim thickness
+ measured value
+ pressure of the tapered-roller bearing
Example
Shim thickness provided 5.00 mm
Measured value 0.75 mm
Pressing (constant value) 0.40 mm
_________
"S"tot = 6.15 mm
- Remove differential, pull off both tapered roller bearings and split calculated shim thickness "S tot." as follows. Select spacer S1 0.70 mm thinner and S2 0.7 mm thicker as a starting point for subsequent adjustment of the flank backlash.
Example
Total shim thickness of spacers
S1 + S2 = 6.15 mm
Thickness of spacer S1
6.15 mm divided by 2 = 3.075 mm
- 0.700 mm
_____________
S1 = 2.375 mm
Thickness of spacer S2
6.15 mm divided by 2 = 3.075 mm
+ 0.700 mm
_____________
S2 = 3.775 mm
NOTE: Spacers are available in thickness 1.6-3.1 mm in increments of 0.10 mm. A 0.25 mm thick shim makes it possible to graduate shim thicknesses in increments of 0.05 mm. The calculated shim thicknesses must be rounded up or down for plausible dimensions, so that the total thickness S1 and S2 does not change.
Example
Calculated thickness
S1 + S2 = 2.375 + 3.775 = 6.15 mm
Rounded off thicknesses
S1 + S2 = 2.35 + 3.80 = 6.15 mm
NOTE: Measure shims with a micrometer in several places. Permissible deviation 0.02 mm. Also check shims for burrs and damage.
Circumferential Backlash Adjustment
NOTE: The backlash to be set is embossed on the ring gear.
- Mount gear set using shims "S3" determined while adjusting the drive pinion.
- Insert differential with tapered roller bearing and shims (S1 + S2) into the housing.
- Fit side transmission cover and tighten all hexagon nuts with 23 Nm (17 ft lb).
NOTE: Always make sure that there is a certain amount of flank backlash when tightening the nuts. Never allow the drive pinion to seize.
- Assemble measuring lever VW 388 and adjusting device VW 521/4 and adjust lever length to 80 mm with the plunger. Refer to dimension "a" in the image.
Insert adjusting device with clamping sleeve (Special Tool 9145) into the differential and clamp firmly.
- Crank differential in both directions several times to settle the tapered roller bearing.
- Screw Special Tool 9283 (without shim "S") onto the hollow shaft hand tight.
Dimension "a" = approximately 80 mm
- Fit universal dial-gauge holder with flat extension in such a way as to produce a right angle between dial-gauge axis and lever.
- Turn ring gear carefully at the clamping screw of the adjusting device as far as the stop and set the dial gauge to 0. Turn back ring gear and read off circumferential backlash. Record the value.
- After turning the ring gear a further 90° repeat measuring procedure three times. The measured values must not deviate from one another by more than 0.05 mm.
NOTE: The backlash to be adjusted is embossed on the ring gear. The actual value may be less than the specified value by 0.05 mm. Under no circumstances may the backlash be greater than the specified value.
If it is not possible to obtain the prescribed flank play, replace spacers (S1 + S2) again. The total shim thickness (Stot.) must not alter however.