Final Drive Unit Clutch Plates
FINAL DRIVE UNIT CLUTCH PLATES
RENEW
To overcome Powr Lok differential noise when cornering, a revised Powr Lok clutch pack has been introduced from VIN 557874. Final drive units incorporating the revised clutch packs are identified by a unit serial number after 88H 75025.
Where Powr Lok differential noise is experienced with final drive units prior to the above serial number the revised clutch packs may be fitted as follows:
Parts Required: JLM 1715 - Clutch Pack Kit comprising:
2 off Grooved tagged plate
2 off Tagged plate
4 off Friction disc
4 off Thin tagged plate
2 off Belville plate
2 off Differential side gear
2 off Lower wishbone stud
- Remove the final drive unit from the vehicle.
- Clean the unit and drain the oil.
- Secure the unit and remove and discard the lower wishbone studs.
NOTE: The final drive unit may be secured to a suitable work bench by drilling 2 x 15 mm diameter holes in the bench 125 mm apart, 75 mm from the edge of the bench and securing with 2 suitable bolts (Fig 1).
- Remove the rear cover.
- Remove the output shaft assemblies from the unit, retaining the shims and shaft assemblies separately for re-assembly into their original positions.
- Mark the pinion flange, main casing and crownwheel with a dab of paint (A Fig 2) to ensure correct reassembly).
- Position a suitable dial gauge as shown in Fig 1 and measure the backlash between the crownwheel and pinion gears at 3 places equally spaced around the crownwheel.
- Record the average of the 3 readings.
NOTE: The pinion should be locked when the backlash is measured.
- Remove the differential bearing caps, noting the markings on the caps and main casing (B Fig 2).
- Fit the main casing stretcher tool (Tool Number GKN 131) as illustrated in Fig 3, position the dial gauge as shown and tighten the clamp nuts to stretch the casing 0.25 mm (0.010").
- Using a suitable lever, displace and extract the differential assembly from the main case.
- Remove the stretcher tool.
- Displace and remove the bearing races from the differential assembly and place aside, suitably marked, to ensure re-assembly into their original positions.
- Place the differential assembly on to a bench and remove the case bolts (1 Fig 1).
- Remove the button half of the differential case (7 Fig 1).
- Mark the cross pin ends and differential case to ensure that the cross pin, pinion mates and thrust washers are all refitted into their original positions during re-assembly.
- Remove the cross pin complete with pinion mates and thrust washers (2,3,5 Fig 1).
- Remove and discard the differential side gear and clutch plate pack from each half of the differential case (4,6 Fig 1).
- Carefully clean all components.
- If the final drive unit serial number is prior to 87E 22566 and had a total of 5 clutch plates each side (including the belville plate), re-assemble the differential assembly clutch packs into the differential casing halves in accordance with Fig 2 (6 plates each side. Note the orientation of the belville plates; discard surplus new plates).
1 Grooved tagged clutch plate - groove towards side gear
2 Friction disc
3 Thin tagged clutch plate
4 Belville clutch plate
5 Differential side gear
NOTE: Each plate should be coated with Shell Spirax Super 90 oil during assembly. The thin plates and belville plates are identified by two diagonally-opposite notches on the circumference of the plate.
- If the unit serial number is post 87E 22565 and had a total of 6 plates each side (including the belville plate) then re-assemble the differential assembly clutch packs into the differential casing halves in accordance with Fig 1. (7 plates each side. Note the orientation of the belville plates).
1 Grooved tagged clutch plate - groove towards side gear
2 Tagged clutch plate
3 Friction disc
4 Thin tagged clutch plate
5 Belville clutch plate
6 Differential side gear
NOTE: Each plate should be coated with Shell Spirax Super 90 oil during assembly. The thin plates and belville plates are identified by two diagonally opposite notches on the circumference of the plate.
- Locate the new differential side gears into the clutch pack splines and refit the cross pin complete with the pinion mates and thrust washers, ensuring that the marks from operation 16 are correctly aligned.
- Refit the button half of the differential case, ensuring that the case markings (8 Fig 1) are aligned and torque the fixing bolts in a diagonal sequence to 67 Nm.
NOTE: Loctite Studlock 273 should be applied to the bolt threads prior to fitment.
- Turn the pinion to align the paint marks on the pinion flange and the main casing.
- Lubricate the differential bearings and locate the bearing races to their original bearings.
- Fit the main casing stretcher tool (GKN 131) to the main casing as illustrated in Fig 2 and tighten the clamp nuts to stretch the casing 0.25 mm (0.010").
- Fit the differential assembly into the main casing, ensuring that the paint marks on the crownwheel and casing are aligned.
- Fit the differential bearing caps, but do not fully tighten the securing bolts. Ensure the markings on the bearing caps and main casing are aligned.
- Remove the main casing stretcher tool from the casing and fully tighten the bearing cap fixing bolts to 122 Nm (90 lbft).
- Measure the backlash between the crownwheel and pinion gears, as shown in Fig 1, at 3 places equally spaced around the crownwheel. Calculate the average of the three readings and compare this with the figure recorded previously.
- The average backlash should be within 0.038 mm (0.001 5") of the original figure.
- Fit the output shaft assemblies and their respective shims into their original sides and torque the fixing bolts to 58 Nm (43 lbf.ft).
NOTE: Loctite Studlock 273 should be applied to the ~ bolt threads prior to fitment.
- Apply Hylosil 101 RTV jointing compound to the rear cover joint face. Locate the cover to the main case and loosely fit the new lower wishbone studs.
- Fit the rear cover fixing bolts and tighten to 29 Nm (22 lbf.ft). Fully tighten the lower wishbone studs to 270 Nm (200 lbf.ft).
- Remove the final drive unit from the bench, ensuring that the oil drain plug is tight and place the unit on to a level surface. Fill the unit to the correct level with Shell Spirax Super 90 oil.
- Refit the final drive unit to the vehicle.
NOTE: To allow sufficient 'bedding in' of the new clutch packs avoid tight turns or figure-of-eight testing for 30 miles.
DATA
Backlash 0.038 mm (0.0015")
Casing 'stretch 'required 0.25 mm (0.010").
TORQUE FIGURES
Bearing cap fixing bolts 122 Nm
Differential case bolts (in diagonal sequence) 67 Nm
Lower wishbone studs 270 Nm
Output shaft bolts 58 Nm
Rear cover fixing bolts 29 Nm
OILS/GREASES/SEALANTS
Differential oil Shell Spirax Super 90