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).
- Fit gear housing and locate with three nuts.
- Install and engage fifth gear.
A = Suitable pipe section or old bushing removed from 5th gear needle roller bearing
- Block input shaft with special tool 9253 and tighten drive pinion collar nut to 250 Nm (183.25 ft.lb).
a = Approx. 65 mm
- Set adjusting ring of measuring mandrel VW 385/1 to dimension "a".
- Assemble measuring mandrel with centering disks 9109, tapered roller bearings, plunger VW 385 /14 and dial gauge extension VW 385/15.
- Set measuring mandrel with master gauge 385/30 to adjusting dimension (61.43 mm in the example). Set dial gauge (3 mm measuring range) to zero with 1 mm preload.
- Put gauge block plate 9281 on drive pinion head and insert measuring mandrel into transmission case. Dial gauge extension is located in the area of the gauge block plate.
- Fit side transmission cover without 0-ring and tighten crosswise with 4 nuts.
NOTE: Do not use a hammer when fitting the side transmission cover (the gauge block plate held by magnets might fall off). Fit cover in installation position only by tightening the nuts uniformly.
- Pull second centering disk with spindle towards the outside until the measuring mandrel can just be turned by hand.
- Turn measuring mandrel carefully until the dial gauge extension is vertical to the face 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 a preload of 1 mm, the value deviating from 1 is taken as shim thickness "S3".
Example: If the small pointer on the dial gauge is between 1 and 2 and the large pointer indicates 0.37 mm, then 0.37 mm is the shim thickness (with 1 mm gage preload) to be inserted. Always round up or down to the nearest 0.05 mm (e.g. 0.37 mm to 0.35 mm).
- After inserting the necessary shims, check the setting value "E" again. A deviation of + 0.03 mm is permissible.
Ring Gear Adjustment
- Determine total shim thickness "S tot." (S1 + S2).
- The ring gear must be adjusted if any of the following are replaced:
Transmission case
Side transmission cover
Tapered roller bearing for differential
Differential housing or drive set
NOTE: The drive pinion must be removed to determine the preload of the differential tapered roller bearings.
- Make sure that the bearing outer races of the tapered roller bearings are well seated in the transmission case or side transmission cover, respectively.
- 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 rotate several times.
- Fit side transmission cover without seal and tighten all hex nuts to 23 Nm (16.9 ft.lb).
- Put gauge block plate VW 385/17 on the collar of the differential.
A = Dial gauge extension (approx. 30-40 mm long)
B = Gauge block plate VW 385/17
- Fasten universal dial gage 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 give an incorrect reading.
- Calculate "S tot".
"S tot" = Fitted shim thickness
+ measure value
+ pressure fit of the tapered roller bearing
Example
Thickness of shims inserted 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 0.70 mm thicker as a starting point for subsequent adjustment of the 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 = 3.075 mm
+ 0.700 mm
___________
S2 = 3.775 mm
NOTE:
- Spacers are available in thicknesses of 1.6 to 3.1 mm in increments of 0.10 mm.
- By using a 0.25 mm shim the shim thicknesses may graduated in increments of 0.05 mm.
- The calculated shim thicknesses must be rounded up or down for plausible dimensions that will not alter the total thickness S1 and S2.
Example
Calculated thicknesses
S1 + 32 = 2.375 + 3.775 = 6.15 mm
Rounded down ring thickness
S1 + 32 = 2.35 + 3.80 = 6.15 mm
- Measure shims with a micrometer in several places. Permissible deviation 0.02 mm. Also check shims for burrs and damage.
Adjusting Circumferential Backlash
NOTE: The backlash to be set is embossed on the ring gear.
- Mount gear set using shims "S3" determined while adjusting the drive pinion.
NOTE: Make sure that the collar nut of the drive pinion is tightened to 250 Nm (183.25 ft lb) before measuring backlash.
- Insert differential with tapered roller bearing and shims (S1 + S2) into the housing.
- Fit side transmission cover and tighten all hex nuts to 23 Nm (16.9 ft lb).
NOTE: Always make sure that there is a certain amount of backlash when tightening the nuts. Never allow the drive pinion to seize.
Dimension "a" = Approx. 80 mm
- 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.
- Rotate differential in both directions several times to settle the tapered roller bearings.
- Fit universal dial gauge holder with flat extension in such a way as to produce a right angle between dial gauge axis and lever.
NOTE: When carrying out measurements, the drive pinion must be blocked with Special Tool 9260.
- Turn ring gear carefully at the clamping screw of the adjusting device as far as the stop, and set the dial gauge to zero. Turn back ring gear and read off circumferential backlash. Note the reading.
- After turning the ring gear a further 90°, repeat measuring procedures 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 the required backlash cannot be obtained, replace spacers (S1 + S2) again. The total shim thickness (S tot.) must not be altered, however.