Final Drive Assembly
GENERAL NOTESCareful adjustment of drive pinion and ring gear is essential for long life and quiet running of the final drive. For this reason, drive pinions and ring gears are matched during the production phase and checked with a special gauging machine to ensure proper contact pattern and quiet running in both directions of rotation. The position of the quietest running is determined by moving the drive pinion in an axial direction, with the ring gear being constancy raised out of zero-play meshing to a point where the torsion backlash varies within a specified tolerance.
The deviation "r" is measured in relation to the master gauge Ro for the drive gear sets supplied as service parts and this value is inscribed on the outer circumference of the ring gear. Each drive gear set-drive pinion and ring gear-must only be replaced together.
ADJUSTMENT AND INSCRIPTION OF DRIVE GEAR SETS
Service Drive Sets
1 - Marking "0937N means: Oerlikon drive gear set with the ratio 37:9 (4.11:1)
2 - Matching number of drive gear set (e.g. 312)
3 - Deviation fir" in relation to master gauge of special gauging machine used in production. Deviation "r" is stated in 1/100 mm. Example: "25N means r = 0.25 mm
Ro - Length of master gauge used on special gauging machine Ro = 53.15 mm
R - Actual dimension between ring gear shaft and face end of d rive pinion at the point of quietest running for this one d rive gear set
Vo - Hypoid offset = 35 mm
Drive Gear Sets In Series Production
Data that is not required for series production is crossed out with an "X" in the illustration.
PO - Setting for series production
CAUTION:
^ In series production the position of the drive pinion is determined by dimension PO (center of ring gear to rear of drive pinion head). Deviation "r" and the matching number of the set are not inscribed on the ring gear.
^ Because the deviation "r" is unknown, an actual measurement must be carried out before removing the drive pinion when parts that directly affect the installation position of the drive pinion are replaced, refer to Drive Pinion Installation Position, Determining By Actual Measurement, below.
LIST OF ADJUSTMENTS
When performing removal and installation work on the final drive, it is only necessary to re-adjust drive pinion, ring gear and flanged shaft if parts which directly affect the setting are replaced. Refer to the table below to avoid unnecessary adjustment operations.
DRIVE PINION INSTALLATION POSITION, DETERMINING BY ACTUAL MEASUREMENT
This operation should only be carried out if deviation "r" is not inscribed on the ring gear, and parts that directly affect the installation position of the drive pinion are to be replaced.
These are:
Tapered roller bearings for drive pinion
Tapered roller bearings for final drive housing
Removing Differential
Set up universal gauging drift, as described under Drive Pinion Adjusting, below. Install into final drive housing and measure difference relative to Ro (take reading of max. deflection/reversal point in red numerical range). The reading obtained corresponds to the deviation "r. " Note the reading.
After replacing the part, the drive pinion should be adjusted as described under Drive Pinion Adjusting, below. The deviation "r" calculated for determining thickness of shim S3, should be used in this case.
Recommended Sequence Of Operations For Re-adjusting Drive Gear Set
If drive pinion and ring gear have to be adjusted, it is recommended to keep to the following sequence of operations in the interest of rational working:
1 - Determine total shim thickness "S total" (S1 plus S2) for specified preload of differential tapered roller bearing.
2 - Determine total shim thickness S3 so that the drive pinion is installed in the position determined on the special gauging machine during the production phase.
3 - Divide total shim thickness "S total" into S1 and S2 so as to achieve the specified torsion backlash between ring gear and drive pinion.
The aim of the adjustment is to re-create the position of quietest running as was determined on the special gauging machine in production.
The maximum care and cleanliness during all removal and installation work and measurement operations are essential for achieving satisfactory results.
LOCATION OF SHIMS
DRIVE PINION, ADJUSTING
(Adjusting output shaft)
It is only necessary to re-adjust the drive pinion as specified in the instructions below if the drive gear set is replaced. If other parts that likewise affect the installation position of the drive pinion are replaced, the adjustment should be carried out using the installation position determined previously (Drive Pinion Installation Position, Determining By Actual Measurement).
List Of Adjustments.
- Clamp final drive.
- Pull large outer race for tapered roller bearing into housing without shim.
- Pull small outer race for tapered roller bearing into housing.
- Install drive pinion.
- Heat inner race for tapered roller bearing to 100°C (212°F), install onto drive pinion without spacer sleeve and press home.
- Tighten drive pinion nut until reaching friction (turning) torque of 280-320 Ncm (25-28 inch lb).
(-A-) Torque gauge, commercially available, 0-600 Ncm (approx. 0-50 inch lb)
(-B-) Extension with 32 mm socket wrench
- Set adjusting ring of measuring bar VW 385/1.
Dimension -a- = 60 mm
- Set movable adjusting ring of measuring bar VW 385/1
Dimension -b- = 50 mm
- Set up measuring bar as illustrated.
Dial indicator extension VW 385/20 = 3 mm
- Set adjustable master gauge VW 385/30 to Ro = 53.15 mm.
- Zero dial indicator with a preload of 3 mm.
- Attach end gauge to drive pinion head.
- Install universal gauging drift.
- Install on cover for final drive and tighten 4 bolts.
- Move the 2nd centering plate to the outside by means of the movable adjusting ring so that it is just still possible to turn the gauging drift by hand.
- Measure size-e-.
Turn gauging drift until the dial indicator tip touches the end plate on the drive pinion head and indicates the maximum deflection (reversal point). The reading obtained is the size -e(red numerical range).
Example: 1.60 mm
CAUTION:
^ Finally-after removing the measuring bar-re-check whether the dial indicator is set to zero with a 3 mm preload with the master gauge VW 385/30 installed.
^ If not, repeat the measurement
DETERMINING THICKNESS OF SHIM S3
S3 = e - r
e - Reading obtained (max. deflection)
r - Deviation (indicated on ring gear in 1/100 mm or determined by actual measurement)
Example:
Reading -e- indicated on dial gauge (example) minus Deviation "r" inscribed on ring gear equals Thickness of shim S3
1.60 mm
+ 0.42 mm
= 1.18 mm
Shims Available As Replacement Part
NOTE: As a result of the tolerances of the shims it is possible to gauge any desired thickness for S3
- Remove measuring bar.
- Remove drive pinion and re-install with calculated size of shim, spacer sleeve and seal, refer to Rear Drive Pinion, Removing/Installing. Service and Repair
- Install flange again, tighten hex nut until reaching specified friction torque.
CAUTION:
^ Slowly increase tightening torque and read friction torque value several times when doing so.
^ If the specified friction torque is exceeded, the spacer sleeve must be replaced and the adjustment repeated.
^ A sleeve that has been compressed cannot be reused.
- The following friction torques should be set:
New bearings:
280 - 320 Ncm (25 - 28 inch lb)
Used bearings: (Bearings that have run at least 50 km (30 miles))
30 - 60 Ncm (3 - 5 inch lb)
Performing Check Measurements
- Check size "R"
- Rotate drive pinion in both directions several times.
- Install measuring bar and carry out check measurement.
If the correct size shim has been selected the dial indicator, when read counter-clockwise (red numerical range) must indicate the value of the inscribed deviation "r" within a tolerance of +0.04 mm.
RING GEAR, ADJUSTING
(Adjusting differential)
It is only necessary to re-adjust the ring gear if the final drive housing, final drive cover, tapered roller bearing for differential, differential housing or drive gear set are replaced.
Refer to List Of Adjustments, above
Determining total shim thickness (S1 + S2)
(Adjusting preload of differential tapered roller bearings)
NOTE: Drive pinion removed!
- Remove seal and outer races for differential tapered roller bearing and take out shims, refer to Overhaul, Final Drive Assembly. Service and Repair
- Drive in tapered roller bearing outer races, without shims, as far as stop, refer to Overhaul, Final Drive Assembly. Service and Repair
- Install differential into housing.
The ring gear is on the right-hand side (cover side).
- Install cover and tighten bolts diagonally to 25 Nm (18 ft lb), cover facing up.
(-A-) Dial indicator extension approx. 30 mm (1-3/16 inch) long
(-B-) 8x45 mm hex bolt
- Install measuring tool.
- Zero dial indicator (3 mm range) with a preload of 1 mm.
- Move differential up and down, read play at dial indicator and note.
Example: 1.60 mm
CAUTION: Do not turn differential when performing measurement otherwise the bearings we shift and the result of the measurement will be falsified.
Determining "S total"(S1 + S2)
Stotal = Result of measurement + compression (a constant value)
0.40 mm (constant value)
+ 1.60 mm Reading (example)
= 2.00 mm = S total
- Install calculated total thickness of shim (in the example 2.00 mm) behind the tapered roller bearing outer race in the final drive housing (S2 side).
- Measure friction torque.
(-A-) Torque gauge, commercially available, 0-600 Ncm (0-53 inch lb)
New bearings:
280 - 320 Ncm (25 - 28 inch lb)
Used bearings: (Bearings that have run at least 50 km (30 miles))
30 - 60 Ncm (3 - 5 inch lb)
NOTE: When re-adjusting the gear set, the drive pinion adjustment with check measurements should now be carried out, refer to Drive Pinion, Adjusting above.
Adjusting Torque Backlash
NOTE:
^ Drive pinion installed with shim S3
^ Differential: S total (S1 + S2) installed on housing side
- Rotate differential several times in both directions so that the tapered roller bearings settle.
- Install measuring tools.
- Use dial indicator extension VW 392/10 (6 mm flat).
Set measuring lever -a- = 79 mm.
- Turn ring gear as far as the stop, zero dial indicator.
- Turn ring gear back, read torque backlash.
Note reading
- After turning ring gear 90� in each case, repeat measurement another three times. Add together the four readings obtained and calculate average torque backlash.
CAUTION: If the individual readings obtained during this measurement differ by more than 0.06mm from each other, either the ring gear or the drive gear set itself is out of alignment Check installation work, replace drive gear set if necessary.
Determining Average Torque Backlash
Example:
1st measurement 0.68 mm
+ 2nd measurement 0.70 mm
+ 3rd measurement 0.70 mm
+ 4th measurement 0.68 mm
= Total 2.76 mm
Average torque backlash equals total divided by four
2.76 / 4 = 0.69 mm
Determining Shim Thickness S1 From Table
S1 Shim Table (Part 1 Of 3):
S1 Shim Table (Part 2 Of 3):
S1 Shim Table (Part 3 Of 3):
Example:
Average torque backlash = 0.69
S1 From Table = 0.78 mm
Available S1 Shims:
- Use the above table of available shims to select the S1 shim
Determining shim thickness S2
(opposite ring gear)
S2 = S total- S1
Example:
Stotal 2.00 mm
- S1 0.78 mm
= S2 1.22 mm
Available S2 Shims:
- Use the above table of available shims to select shim S2
- Install calculated size of shims, S1 on ring gear side, S2 opposite ring gear.
Check Measurement
- Measure torque backlash four times around circumference.
This must be 0.12-0.22 mm.
CAUTION: The individual results must not differ by more than 0.05 mm from each other.