Disassembly/Adjustment/Assembly of Front/Rearlocking Plates

Disassembly/Assembly

Front/Rear Locking Plates Assembly:

Legend:

- Refer to images for instructions and legends.

Additional Disassembly Steps

- Remove snap ring (No. 19) through the assembly holes in the clutch sleeve with a suitable tool.

- Remove collar nut (No. 23) with Special Tools 9275, 9276 and 9280.

- Remove inner bearing race (No. 26) with Special Tools 9278 and 9294.

- Remove lock nut (No. 29) with Special Tools 9276 and 9277.

- Pull out Inner bearlng race (No. 28) over the bearing carrier with Special Tool 9294 and a suitable puller.

NOTE: Counternut (No. 29) must be unscrewed beforehand.

Modifications from 1991 Model On (Applicable to all models)

A = Installed position

- Before dismantling the transmission always measure the amount of wear on the front-rear locking plates. If plates are re-used after having been operated for a period, the bearing pin of the counter-bearing bolt must remain in the same position as before. If it has to be reset or if the counter-bearing bolt has to be removed (for instance to rectify a leak) the correct position for re-installing must first be determined.

Measuring The Disk Wear On The Longitudinal And Transverse Locks

Note: The wear dimension can be determined only with the lock measuring cylinder, special tool 9514.

Explanation of special tool 9514
^ The scope of delivery of special tool 9514 comprises the parts A-B-C. The assembly consisting of A-B-C is used for transverse lock measurement. Only Part A is needed for longitudinal lock measurement.

Front/Rear Locking Plates Assembly:

Legend:

- Refer to images for instructions and legends.

Additional Disassembly Steps

- Remove snap ring (No. 19) through the assembly holes in the clutch sleeve with a suitable tool.

- Remove collar nut (No. 23) with Special Tools 9275, 9276 and 9280.

- Remove inner bearing race (No. 26) with Special Tools 9278 and 9294.

- Remove lock nut (No. 29) with Special Tools 9276 and 9277.

- Pull out Inner bearing race (No. 28) over the bearing carrier with Special Tool 9294 and a suitable puller.

NOTE: Counternut (No. 29) must be unscrewed beforehand.

Modifications from 1991 Model On (Applicable to all models)

A Measuring cylinder
B Flange for transverse lock testing
C Flange securing nut

1 Spacer tappet
2 Adjusting screw
3 Two surfaces for fixing the measuring cylinder for longitudinal lock measurement
4 Measuring groove on adjusting screw
5 Separating line for LS and QS measuring ranges
6 LS = Longitudinal lock measuring range
7 QS = Transverse lock measuring range (also for PSD of 928)

Preliminary work

NOTE: Before testing, check if Valeo discs are fitted. Initial version had Gylon discs installed. Identification: "V" embossed on transmission housing flange bottom that the lock cylinder is fitted to. Modified/present version (Valeo discs) were introduced for production as of 01-01-91. As of transmission No. G 64 00 01146/ G 64 01 30 00529/ G 64 02 30 00501. Only Valeo discs are available now.

1. To prevent the measured result from being corrupted, close the locks 2 times at full booster pressure before measurement.
To do this:
- Switch on the ignition
- Press the brake pedal as often as required until the pump assembly starts running.
- When the pump assembly has switched off independently, turn the full-lock switch (traction switch in the center console) to the right (close lock). Then turn the switch to the left (open lock)
- Repeat this operation, i.e. close and open the locks once more.
- Switch off the ignition.
2. Depressurize the booster circuit for safety reasons. To do this, remove the ignition key and then operate the brake pedal approx. 25 times.

3. Remove the slave cylinders
- Transverse lock: Undo the fixing screws on the slave cylinder. Do not undo the pressure line.
- Longitudinal lock: Unscrew the screw on the slave cylinder and pull out holding plate (arrow). Do not undo the pressure line.
- Unclip the pressure line at the transmission and hang both lock cylinders to the side with connected line.

Measurement

NOTE: Perform measurement only after completion of all preliminary work. The sealing bellows (A) in the transmission case remains installed for measurement on the longitudinal and transverse locks.

1. Back off the adjusting screw of the measuring cylinder (2) as far as possible so that assembly of the measuring cylinder is made easier.

2a. Measure transverse lock. Fit the measuring cylinder (A) with flange (B) on the transmission. Align the measuring cylinder so that the measurement scale is easily visible. Tighten the flange securing nut (C).

2b. Measure the longitudinal lock. Secure the measuring cylinder with holding plate for the slave cylinder (arrow) on the transmission.
3. Screw in the adjusting screw (2) on the measuring cylinder until there is no axial play at the spacer tappet (1) or so that there is just minimally perceptible axial play. Read off the axial dimension on the measuring cylinder in this position. If the wear dimension has been reached, the disks of the lock must be replaced.

NOTE: If the first bearing screw of the engaging lever is adjustable, do not correct (manipulate) the wear dimension at the screw under any circumstances. In contrast, the adjustment dimension must be produced with the adjustable thrust bearing screw when new disks are installed.

Adjustment And Wear Dimension In mm:

4. If the disks are Ok, assemble the slave cylinders on the transmission again.

NOTE: If the sealing bellows leaks, always replace the corresponding slave cylinders as well. In this case, bleed the lock cylinders and pressure line with system tester 9288 afterwards.

5. Check general operation of the lock (brief test drive).
Assembly

A = Missing tooth
B = Spiral groove
C = Oil hole

- Apply a film of transmission oil to Inner plates and assemble so that the spiral groove for the oil supply runs counterclockwise from inside to outside when looking at the clutch sleeve (direction of assembly) (refer to the simplified sketch). Apart from this, the oil holes in the carrier plate must be in line with one another. Assembly is easier if a tooth is missing from the carrier plate.

A = Tab washer

B = Lugs of tab washer

- Insert tab washer (A) between 3rd and 4th inner plate so that the lugs (B) project through two oil holes in the carrier plate.

A = Pressure plate
B = Engaging fork
X = approx. 8 mm

- Insert pressure plate (No. 13) into transfer case in correct position (recesses on bearing must latch into the driving journals of the engaging fork).

NOTE: The pressure plate is in the correct position if dimension "X" is approx. 8 mm.

- Mount transfer case and pressure plate carefully. Turn input shaft so that the teeth on the pressure plate engage with the teeth of the clutch sleeve.

NOTE: The transfer case is in the correct position if it can be slid up completely by hand. If there is a gap of approx. 6 mm between transfer case and intermediate housing, the teeth of the pressure plate have not engaged into those of the coupling sleeve.

A = Tensioning plate
B = Eccentric bush

- Adjust the inner shift rod with eccentric bush (No. 4) in such a way that it is possible to preselect all gears without resistance. For this, undo hexagon head screws holding the tensioning plate and turn the eccentric bush.
- Change through all gears by way of a check. For this, fit long M 8 screws into the inner shift rod.

Determining Thickness Of Plate Cluster (with Gylon discs)

- If the plates for the front-rear lock are renewed, the plate cluster thickness must be determined.
^ Adjustment value (new) = 26 - 0.2 mm

^ Wear limit = 23 mm

NOTE: If the wear limit is reached, replace all inner discs.

- Measure entire disc pack.

Example I
Measured value 106.90 mm
Height of special tool - 81.50 mm
___________
Plate cluster thickness 25.40 mm

NOTE: Height of special tool is marked on the tool

Adjustment value 26.00 mm
Plate cluster thickness - 25.40 mm
____________
Adjusting plate 0.60 mm

Example II
Measured value 106.00 mm
Height of special tool - 81.50 mm
___________
Plate cluster thickness 24.50 mm

NOTE: Height of special tool is marked on the tool

Adjustment value 26.00 mm
Plate cluster thickness - 24.50 mm
____________
Adjusting plate 1.50 mm

NOTE: Do not install any outer adjusting plates thinner than 1.3 mm. In Example I, one of the six 1.3 mm thick outer plates must be increased in thickness by 0.6 mm (to 1.9 mm). In Example II, an additional outer plate 1.5 mm thick must be inserted between the inner plate and the pressure plate.

Adjusting Counter-Bearing For Front-Rear Lock

NOTE: Adjustment is possible only with the measuring cylinder (special tool 9514), and is only necessary if the plates are renewed.

1. The flexible gaiter for the slave cylinder must be installed.
2. Slacken off the measuring cylinder adjusting screw as far as possible (to make it easier to install the measuring cylinder).
3. Attach the measuring cylinder to the transmission.
4. Use the adjusting screw to set the measuring cylinder to 29.5 mm (in the front-rear differential lock measuring range). LS = Front-rear diff. lock measuring range OS = Lateral diff. lock measuring range

1 Spacing plunger
2 Adjusting screw
2a Measuring groove on adjusting screw
3 Special tool 9514/1
4 Locknut (seal with Loctite 222)
5 Bearing pin (counter-bearing)

5. Screw in the bearing pin until there is no more endplay at the measuring cylinder spacing plunger. In this position, lock the bearing pin with the hex nut. Tightening torque: 40 Nm (30 ft lb.

Modifications To The Longitudinal Lock

Following introduction of the Valeo inner discs, the number of discs and the stacking of the disc pack have been modified.
1 Wave disc
2 Valeo inner disc
3 Outer disc (1.3 mm thick)
4 Outer adjusting disc
5 Snap ring
6 Thrust plate

NOTE: Due to the fact that supply of the Gylon inner discs is stopped, the longitudinal lock must be fitted with Valeo friction discs if repairs are required. To do so, replace all friction discs as well as the wave disc and adjust the pack thickness to the specified dimension (26 mm). Combining Gylon and Valeo inner discs is not permissible.

Determining Disc Pack Thickness (with Valeo inner discs)

NOTE: Due to the transition from Gylon to Valeo inner discs, the stacking of the disc pack has been modified.

Former Gylon Disc:

New Valeo Disc:

1. Determine thickness of disc pack.
- Pack thickness (new) = 26.0 - 0.2 mm
- Wear limit = 25.2 mm

A = Wave disc

2. Measure entire disc pack with wave disc.

Example
Measurement 106.60 mm
Special Tool height - 81.50 mm
_________
Pack thickness 25.10 mm

NOTE: Special tool height is engraved on the tool. If the wear limit has been reached, all inner discs must be replaced.

3. Adjust to specified pack thickness (26.0 - 0.2 mm) at the thrust plate, using the outer adjusting disc.
4. Apply a thin coat of transmission oil to discs before fitting them.
5. Oil bores in carrier plate of inner discs must line up exactly.