Adjusting Ring Gear
Adjusting Ring GearNote: The ring gear has to be adjusted, if transmission case, final drive cover, tapered roller bearings for differential and/or pinion/ring gear set are replaced (also refer to "necessary adjustments")
Determining Total Shim Thickness "S tot" (S1 plus S2)
(For determination of pre-load for tapered roller bearings on differential.)
1. Remove drive pinion.
2. Remove seals for shaft flanges.
3. Remove outer races of tapered roller bearings for differential. Take out shims.
4. Drive in tapered roller bearing outer races without shims against stop.
5. Place differential in case. Installed position: ring gear facing cover.
6. Install cover and tighten bolts crosswise to 25Nm (18 ftlb).
7. Clamp transmission in assembly stand with cover facing up
A = Dial gauge extension approx. 30 mm
8. Place gauge plate VW 385/17 on collar of differential.
9. Mount universal dial gauge holder VW 387 with dial gauge and extension on case and set dial gauge to zero with 1 mm pre-load.
10. Move differential up and down, read play on dial gauge and note value (e.g. 1.42 mm).
A = Dial gauge extension approx. 30 mm
Note: Do not turn differential while measuring play, since this would cause wrong results.
"S tot" = measured value + pre-load
Example:
Measured value (example) 1.42 mm
Pre-load (constant value) + 0.50 mm
S tot 1.92 mm
11. Install shims with determined total shim thickness (1.92 mm in example) behind tapered roller bearing outer race in cover (S2 side). Lubricate both tapered roller bearings with hypoid oil.
12. Mount cover again.
13. Guide adjusting device VW 521/4 with sleeve VW 521/8 into neck of differential and clamp.
A = Torque meter, standard, 0... 600 Ncm
14. Place 0 to 600 Ncm torque meter on adjusting device and turn slowly and uniformly. The friction torque of new tapered roller bearings must be at least 250 Ncm.
Friction torque of used tapered roller bearings need not be measured.
Note: When adjusting the pinion/ring gear set, now check the drive pinion adjustment.
Adjusting Backlash
Note: Drive pinion to be adjusted and installed with S3 and S4. Turn differential several times to pre-load and settle tapered roller bearings.
1. Place adjustable lever VW 388 on adjusting device VW 521/4. Lever length via large hexagon surface 79 mm to upper edge of ball.
2. Apply universal dial gauge holder with dial gauge and extension so that there is a right angle between the dial gauge axis and lever.
a = 79 mm
3. Turn differential counterclockwise with adjusting device VW 521/4 carefully until ring gear rests on the drive pinion.
4. Now set dial gauge to zero with 2 mm pre-load.
5. Turn differential clockwise until ring gear makes contact with the opposite flank of the next drive pinion tooth. Read backlash and note value.
6. Repeat measurement three times, turning the ring gear 90° further each time.
7. Add the four measured values and calculate the mean backlash value
Determining Mean Backlash
Example:
1st measurement 0.84 mm
2nd measurement 0.85 mm
3rd measurement 0.84 mm
4th measurement 0.83 mm
Sum 3.36 mm
Mean backlash = 3.36 mm divided by 4=0.84 mm
Note: If the measured values deviate from each other by more than 0.06 mm, installation of the ring gear or pinion/ring gear set is not correct. Check installation, replacing pinion/ring gear if necessary.
Determining Shim Thickness S2 (Opposite Ring Gear)
S2 = S tot
+ Lift (axial displacement of ring gear from mesh free of play to attain backlash)
- Measured mean backlash
S tot = total shim thickness S1 + S2
Lift = 0.15 mm (constant value)
Example:
Stot 1.92mm
Lift + 0.15mm
Mean backlash - 0.84mm
S2 1.23mm
Shims Available:
It is possible to have exact shim thicknesses due to the different tolerances.
Determining Shim Thickness S1 (Ring Gear Side)
S1 = S tot - S2
Example:
Stot 1.92mm
S2 - 1.23mm
S1 0.69mm
Shims Available:
It is possible to have exact shim thicknesses due to the different tolerances.
Measure thickness of shims at many different points with a micrometer. Also check shims for burrs and damage.
Only install shims in perfect condition. Install determined shims S1 and S2.
Checking:
Measure backlash on periphery four times.
It should be:
0.10mm to 0.20 mm.
Note: Measurements must not deviate from each other by more than 0.05 mm.