Gear Case

NOTE: Component identifier numbers used in the following illustrations relate to specific steps in the procedures below.





NOTE: The transmission must be fully dismantled.

Disassembly
1. Unhook the throttle cable from the cam and press the cable out of the cover using a suitable jointed wrench.
Wrench size = 11 mm.
2. Undo the cylinder screw and remove the bracket.
Wrench size = TORX socket - TX27
3. The throttle cam can now be removed together with the side spring and shaft.





4. Undo both cylinder screws and remove the locking spring.
Wrench size = TORX socket - TX27
5. Remove the locking pin.
6. Lift the gear selector cam from the pin.
7. Remove the pin.
8. Unscrew the plug and withdraw the support shaft.
Wrench size = 6 mm Allen key
9. Using a drift, tap out the dowel far enough to enable the selector shaft to be withdrawn.
10. Remove the segment with the pawl cam and the shims by pressing the pawl down slightly.
11. The entire unit can be dismantled by unhooking the spring from the segment and withdrawing the pin.
12. Undo the screw, withdraw the pin beside the ring groove and remove the pawl with side spring.
Wrench size = TORX socket - TX27





13. Pull off the outer bearing race using puller tool No. 87 91 675 and holder tool No. 87 91 683, or equivalents.
14. Remove the selector shaft seal.
15. After undoing the screw, remove the dipstick tube.
Wrench size = TORX socket - TX27
16. Remove the fluid pipes.
- Use slide hammer tool No. 87 91 360, or equivalent.

NOTE: Do not damage the seal surface on the gear case.

17. When cleaning the gear case, all plugs must be removed.
18. On models with turbocharger, the fixing pin and pipe (external charge pressure supply) are not normally removed from the gear case.





Assembly

1. On models with turbocharger, if required, the pipe (boost pressure supply) should first be driven into the gear case as far as possible using a plastic hammer.
2. On all models, screw in the plugs with new seals.
Wrench size = 5 mm Allen key
Tightening torque: 15 Nm (11 ft. lbs.)
3. Screw in the two plastic plugs on both sides of the connection holes for the fluid cooler pipes.
4. Turn the gear case one quarter turn and tap in the guide pin using a plastic hammer until only 10 mm (0.39 inch) protrudes.
5. Install the tapered roller bearing race.
The gear case must be heated to about 70° C using a hot air gun. Alternatively, the bearing race can be pressed in using a press.





6. Lubricate a new seal using Vaseline and tap it into place using a suitable sleeve.
7. Install the spring onto the pawl as illustrated.
8. Install the pawl and press in the shaft from the side.
9. Secure the pin in the groove by installing the plate with the screw.
Wrench size = TORX socket - TX27
Tightening torque: 10 Nm (7.3 ft. lbs.)
10. Assemble the segment and the pawl cam by first installing the pin into the pawl cam.

NOTE: The pin must not be installed any other way.

11. Assemble the pin and the pawl cam and segment, turn the parts and install the washer.
12. Then insert the spring through the pin and install it to the segment.
13. Install the entire unit by keeping the pawl depressed and pressing in the support shaft as far as it will go.





14. Screw in the plug with a new seal.
Wrench size = 6 mm (0.24 inch) Allen key
Tightening torque: 32 Nm (23 ft. lbs.)
15. Install the pin into the gear case and install spring in gear position tool no. 87 91 493, or equivalent.
16. Tap the roller into the locking spring using a plastic hammer.
17. Press the guide pin into the gear case and install the locking spring.
18. Press the locking spring against the spacer piece and secure it in this position using two screws.
Wrench size = TORX socket - TX27
Tightening torque: 10 Nm (7.3 ft. lbs.)
19. Press the selector shaft into the segment.

NOTE: The thread must not be damaged.

20. Press the locking spring out and place the selector cam on the pin.
21. Align the selector cam and the segment teeth so that they intermesh.
- Set the selector cam as illustrated.





22. Check and adjust selector shaft clearance.
a. Screw adjusting clearance support tool No. 87 91 501, or equivalent, onto the housing and press the cam against the recess in the pawl cam until there is no clearance.
b. Measure dimension X between the housing and the cam using a fever gauge.
c. Calculate shim thickness "S" using the following formula:
S = X mm (inch) - 10 mm (0.0039 inch)
S = shim thickness
X = measured reading
0.10 mm (0.0039 inch) = selected clearance
Example:
Using a feeler gauge, dimension X is measured as 2.3 mm.
S = 2.3 mm - 0.10 mm = 2.2 mm
Insert 2 shims with total thickness S = 2.2 mm.





23. Install the shim(s) between the segment and housing.
- Before this, the parking pawl washer must again be removed and the selector shaft be withdrawn.
24. Tap in the dowel using a suitable drift so that the open side is positioned at right angles to the selector shaft.
25. Install the side spring to the throttle cam as illustrated.
26. Insert the throttle cam in the accelerator cam and side spring.
27. Install the entire unit.
- Install the retaining plate into the groove in the throttle cam and secure it with the screw.
Wrench size = TORX socket - TX27
Tightening torque: 10 Nm (7.3 ft. lbs.)
28. Press the new throttle cable into the gear case.
29. Tension the throttle cam by turning it through one revolution and placing the cable nipple in the cam.
30. Install the first pipe to the governor and drive it in as far as possible using a plastic hammer.

CAUTION:
^ If the pipe is so deformed that it does not exactly install the pattern of holes, the pipe should be thrown away.
^ Otherwise, there is a danger of the sharp edges on the pipe shaving off swarf from the holes.
^ This swarf will then destroy the transmission.
^ This also applies to the next point.

31. Install the second pipe to the governor.
- Use installing stand tool No. 87 91 790, or equivalent, and drive it in as far as possible using a plastic hammer.
32. Install the dipstick tube.