With my 2012 S3 R400D at 8 years old and 34,000km of which about 5,000km has been track days and the preload on the LSD below 20lbft, it is time for a rebuild as my main winter project this year.
Although there are various methods of removing the diff, the method I use is to remove one wheel and the hub, brake disc, ear and driveshaft on that side. The A-frame and rear anti-roll bar also need to be removed to drop the diff. I have the car stored in the winter on a steel frame that is 1.5m above the ground but is up against the wall on the left side, so this method works well when the car is high enough.
After the right rear wheel was removed, the A-frame was removed, making note of the number of shim washers on each side:
The end links on the anti-roll bar were disconnected by removing the locking clip on the spherical joint attached at the hub carrier end, the four bolts attaching the anti-roll to the chassis tubes were then unbolted and the bar was extracted out the right side:
The brake caliper was then unbolted at the sliders and tie-wrapped to the coil spring (I have the flexible rear brake lines, if not the brake pipe needs to be carefully bent to lift the caliper off the brake disc):
After removing the two rearward hub carrier nuts that also secure the ear to the deDion tube, together with the two rear bolts that attach the ear to the deDion tube and unscrewing the speed sensor and moving it out of the way, the driveshaft, brake disc, deDion ear and hub can now be extracted, the two left hand ear attachment bolts are shown screwed loosely in place after removal, so I don't misplace them, something I tend to do with most bolts as I work:
The driveshaft bolts are now removed, I place a conventional Allen key in the bolt above the one I'm loosening to stop the shaft rotating as I use the hex socket key with my ratchet and an extension:
The lower diff carrier bolts are now loosened, making note of any shim washers between the chassis and carrier, but kept hand threaded in place until the diff is lowered:
Now the top carrier bolt is removed, making note of the shims on each side between the carrier and chassis. My bolt came out fairly easily with a few light taps from a mallet and a rod inserted to drive the bolt out. The diff can now be lowered with your equipment of choice. I used my wheeled tool box with a hydraulic floor jack, using it's natural arc to move the diff sideways as it was lowered, enabling the left driveshaft to be extracted from the diff, but left in place:
With the diff on the bench, the top carrier bolt, 6 hex bolts and top Allen bolt are removed and a thin blade inserted at the top to break the sealant bond to remove the cover:
The side seals can now be removed, preferably with a seal hook tool to avoid any contact with the bearing. A large pair of circlip pliers is now needed to remove the locking circlip. Be careful to mark these clips, they have a specific thickness on each side to give the correct crown wheel and pinion mesh. My driver's side (left side being in Canada) circlip is marked as 3.44mm thick, my passenger/right side is 3.62mm thick. After removing the circlip the outer bearing races can be extracted using finger pressure and sideways movement of the crown wheel and LSD, no tapping or levering required on my diff:
After both external races have been removed the crown wheel and LSD can be carefully rotated and extracted:
The 6 Allen bolts holding the LSD cap in place can now be removed. Make note of the alignment dot on the cap (it is obscured by the ratchet in this picture, but you can see the matching dot on the LSD casing just below the ratchet head). The cap is a fairly tight fit, so three of the Allen bolts can be used in the threaded holes to lift it against the casing by tightening them gradually in sequence.
Now the guts of the LSD can be extracted, laid out in order, cleaned and inspected. The parts order in mine are as follows, bearing in mind the number and thickness of shims can vary, listed from left-hand side (closest to casing cap):
- Thrust shim for diff gear, diff gear Belleville washer, diff gear thrust washer (with the 2 tabs, depressed face towards gear).
- Clutch pack Belleville washer, clutch pack shim, 1st clutch pack steel disc (6 tabs), 1st clutch pack friction disc (carbon or sintered), 2nd clutch pack steel disc, 2nd clutch pack friction disc, 1st LSD cup/cage (marked as L.H.).
- Left hand diff gear, 4 spider gears with 2 cross shafts, right hand diff gear.
- 2nd LSD cup/cage (marked as R.H), 3rd clutch pack friction disc, 3rd clutch pack steel disc, 4th clutch pack friction disc, 4th clutch pack steel disc, clutch pack shim, clutch pack Belleville washer.
- Diff gear thrust washer (depressed face towards gear), diff gear Belleville washer, thrust shim for diff gear.
The ramp angles for my diff are either 30/90 or 45/60, depending on which depression the spider gear shafts are placed in, I will probably stay with 30/90 for most aggressive locking on acceleration and zero on deceleration:
My inspection found the following:
- All ball bearings, races gear teeth and sliding surfaces are clean, bright and show no noticeable wear.
- There was some "paste" from friction plate wear on the bottom of the diff case and in the nooks and crannies of the cups/cage, but not evident elsewhere.
- One friction plate on each side was almost totally worn out, but the other friction plate on each side had only a small amount of wear.
- Both of the clutch plate Belleville washer were in good condition.
- Both diff gear Belleville washers (the small ones) had wear on the surface and one was cracked through, but still in one piece. I will do some measurements when I refurbish the diff and determine if the thrust shims need to be reduced or eliminated.
Left side friction plates:
Right side friction plates:
Cracked thrust Belleville washer:
As my diff has been quiet and really predictable on the track with smooth locking and the condition of the diff besides the plates and thrust Bellevilles, I've just put in an order with Caterham for the £426 sintered plate rebuild kit (no VAT for my Canadian order). The Titan rebuild kit is about 2/3 the price, but doesn't include any shims, whereas the Caterham kit provides a whole set that will allow fine tuning of the clutch pack preload,