DEDICATED LOW RANGE GCD INSTALLATION MANUAL

DISASSEMBLY

THIS SEQUENCE APPLIES ONLY TO MANUAL/MECHANICAL TYPE TRANSFER CASE.

A 75 series low range GCD can be installed into a 78 series transfer case by replacing the 78 series idler gear with a 75 series idler gear.

• LOW RANGE OUTPUT GEAR
• 75 SERIES: 38 TEETH; 78 SERIES: 41 TEETH

NOTE: Transfer case does not need to be removed from the vehicle for GCD installation.

1. REMOVE FRONT AND REAR PROP SHAFTS

2. MEASURE TRANSFER TURNING TORQUE With the gearbox in neutral and transfer in LOW, measure the turning torque and record the result.

3. REMOVE FRONT AND REAR COMPANION FLANGES.

• (a) Using hammer and chisel release staked part of nut.
• (b) Using SST hold the companion flange whilst removing lock nut.
• (c) Remove the companion flange from shaft.

4. REMOVE THE DRIVE SHIFT LEVER AND DUST BOOT.

5. REMOVE 4WD INDICATOR LIGHT SWITCH. Re-use as oil plug. Switch will not be needed with vehicle in constant 4WD. NOTE: The wires can be bridged to provide the dash indicator light.

6. REMOVE THE PLUGS, SPRINGS AND LOCKING BALLS. (Mechanical shift type only) Replace the screw plug only. Other items not required with GCD.

7. REMOVE SPEEDO DRIVEN GEAR AND CABLE.

8. REMOVE POWER TAKE-OFF COVER. This allows access to the transfer case bolts.

9. REMOVE REAR OUTPUT SHAFT REAR BEARING RETAINER.

• (a) Remove and retain speedo drive gear.
• (b) Spacer is NOT required with GCD.

10. REMOVE IDLER GEAR SHAFT LOCK PLATE.

11. REMOVE TRANSFER REAR CASE.

• (a) Remove the bolts
• (b) Using a plastic hammer split and remove the transfer case half.

NOTE: Use extreme caution in splitting the case, keeping the split even so that the case does not jam. The separation is helped by tapping the idler shaft in.

12. REMOVE REAR OUTPUT SHAFT ASSEMBLY. Remove shift fork and shaft and slide out assembly. Shift fork and shaft are not needed with GCD. NOTE: Gear box must be in neutral.

13. REMOVE IDLER SHAFT O-RING.

14. REMOVE REAR OUTPUT SHAFT FRONT BEARING RETAINER.

15. REMOVE CLUTCH SLEEVE WITH SHIFT FORK AND SHAFT. Discard these parts as they are not needed with the GCD.

16. REMOVE FRONT OUTPUT SHAFT. A new shaft is supplied with the GCD.

NOTE: If the transfer case is new or near new the bearing and seal need not be disturbed.

17. REMOVE TRANSFER HIGH AND LOW SHIFT OUTER AND INNER LEVER. Discard these parts.

NOTE: A WELSH PLUG is provided in the KIT to block off the shaft hole.

18. REPLACE REAR OUTPUT SHAFT FRONT BEARING OUTER RACE. A new cup is supplied in GCD KIT - No. 30209.

19. REPLACE REAR OUTPUT SHAFT REAR BEARING OUTER RACE. A new cup is supplied in GCD KIT - No. 32010X.

(a) Install the ORIGINAL shim into the rear bearing retainer.

Go to GCD low range exploded drawing ...

ASSEMBLY

1. REPLACE FRONT OUTPUT SHAFT OIL SEAL. (Only if necessary).

2. REPLACE THE FRONT OUTPUT SHAFT BEARING. (Only if necessary)

• (a) Remove the oil seal.
• (b) Using a screwdriver, remove the snap ring.

3. INSTALL NEW GCD FRONT OUTPUT SHAFT. Using a plastic hammer, drive in the front output shaft until the flange, nut and washer can be started. Pull shaft through with the nut. Remove the nut, apply Loctite and torque up tight.

4. REPLACE FRONT DRIVE SHIFT FORK OIL SEAL WITH 35MM WELSH PLUG. Supplied in GCD KIT for this purpose.

5. REPLACE TRANSMISSION REAR OIL SEAL. (Only if necessary) Apply MP grease to the oil seal.

6. REPLACE REAR OUTPUT SHAFT OIL SEAL. (Only if necessary) Apply MP grease to the seal lip.

7. REPLACE HIGH AND LOW GEAR SELECT OIL SEAL WITH 13MM WELSH PLUG Supplied in the GCD KIT for this purpose.

8. REPLACE SPEEDOMETER DRIVEN GEAR OIL SEAL. (Only if necessary) Oil seal depth: 20mm (0.79 in).

NOTE: A pre-assembly of the transfer case is necessary to set the output shaft preload correctly.

9. INSTALL REAR OUTPUT SHAFT FRONT BEARING RETAINER WITH NEW BEARING CUP IN PLACE.

10. INSTALL INTEGRAL GCD REAR OUTPUT SHAFT ASSEMBLY.

11. INSTALL TRANSFER REAR CASE.

• (a) Stick thrust washer onto transfer rear case with MP grease.
• (b) Place new gasket on the front case.
• (c) Install the rear case.

12. INSTALL SPEEDOMETER DRIVE GEAR.

NOTE: Original spacer is no longer needed.

13. ADJUST REAR OUTPUT SHAFT PRELOAD.

• (a) Install the rear output shaft rear bearing retainer.

NOTE: Align the bearing retainer rib with the case.

• (b) Torque only two of the bolts as follows:TORQUE: 350kg-cm (25ft-lb, 34Nm)

14. TEMPORARILY INSTALL THE REAR COMPANION FLANGE LOCK NUT.

• (a) With the gearbox still in neutral and using a torque meter, measure the rear output shaft preload (turning torque). and compare it with the measurement taken before the transfer was disassembled.
• (b) If the preload does not fall within the specifications, remove the bearing retainer and alter the shims under the bearing cup.
• (c) When the rear output shaft preload is correctly adjusted, torque up the four remaining bolts.

15. INSTALL IDLER SHAFT O-RING AND LOCK PLATE.

• (a) Align the shaft groove to the bolt hole.
• (b) Install O-ring on the shaft groove.
• (c) Using plastic hammer, drive in the shaft.
• (d) Install the lock plate and bolt. TORQUE THE BOLT: 130 kg-cm (9 ft-lb, 13Nm)

16. INSTALL FRONT AND REAR COMPANION FLANGES.

• (a) Install the companion flange.
• (b) Using SST to hold companion flange, install the companion flange lock nut. TORQUE: 1,300 kg-cm (94 ft-lb, 127Nm)
• (c) Stake companion flange lock nut.

17. INSTALL POWER-TAKE-OFF COVER.

• (a) Install the cover with gasket.
• (b) Apply liquid sealer to the two bolts and install and torque as follows: TORQUE: 170 kg-cm (12 ft-lb, 17Nm)
• (c) Install and torque the other bolts. TORQUE: 195 kg-cm (14 ft-lb, 19Nm)

18. INSTALL SPEEDOMETER DRIVEN GEAR. TORQUE: 130 kg-cm (9 ft-lb, 13Nm)

19. INSTALL FRONT AND REAR PROP SHAFTS.

GCD OPERATIONAL TEST

The GCD is designed to un-lock and re-lock the common drive to front and rear axles when one axle attempts to overdrive the other axle during cornering.

NOTE:     The above de-coupling action operates in both forward and reverse gears.

DE-COUPLE SIMULATION

1.  With the vehicle chocked for safety at the REAR wheels raise the front axle wheels off the ground.

2.  FIRST LIGHTLY rotate the PROP- SHAFT of the raised axle both clockwise and anti-clockwise.

     Observation:  The transfer case common axle drive should be solid and not capable of independent drive.

3.  NOW FIRMLY rotate the driveshaft of the raised axle and the de-coupling can be felt as the prop-shaft breaks out and spins freely.  Reverse the rotation of the raised axle prop-shaft and the re-coupling will occur.

4.  Lower the raised axle and repeat the steps to check the REAR axle.

FOR OPTIMUM PERFORMANCE

NOTE: 

1. It is very important that all 4 wheels are of matching diameter for optimum traction and performance.
2. During cornering, the GCD can be heard indexing as it un-locks and re-locks. This is quite normal.      

GCD KIT  PARTS LIST

• 1  x    GCD unit comprising of case, CDA assembly and rear output shaft assembled complete with bearing cones.
• 1  x       Bearing cup       -            30209
• 1  x       Bearing cup       -            32010X
• 1  x       Front output shaft
• 1  x       Welsh plug   ...   -       .   35mm
• 1  x       Welsh plug   ...   -      ..   13mm
• 1  x       Gasket               -            36143-60030
• 1  x       Gasket               -            36143-60020
• 1  x       Instruction Manual
• 1  x   ... Caution sticker

return to Gearing Dynamics Home page                                    Go to GCD low range exploded drawing