Cleaning & Rebuilding the Drivetrain

Well having invested in a new can of Tetraclene I set about cleaning up the last 20% of the car, This basically meant the rear suspension, the rear half of the engine bay and the diff carrier, all of which were covered in a thick layer of lithium grease and chain lube. The car came up very nicely. However I was having difficulty getting at the areas around the diff and chain wheel carrier, so I decided to remove the entire unit from the car. This was a fairly radical decision, as it meant removing the drive shafts from the diff, and If I had a problem I wouldn't be able to roll the car back in the garage very easily, but taking the diff out has a number of advantages.

1. I'll learn how the drive train is put together, nothing teaches you this better than a disassemble\reassemble cycle.
2. I'll also learn how to remove the drive shafts and how the rear suspension goes together.
3. It will give me a chance to check and paint the diff carrier, fit the handbrake calliper, and lubricate the Quaiffe ATB diff unit in the centre of it all. And I get to do all this at a comfortable bench height.

All good reasons to bite the bullet, besides as I'm used to car diffs with crown wheels, pinions and oil baths I was intrigued by how the unit went together when the drive was provided by a chain rather than a propshaft.

So first job was to remove the drive shafts, I guessed that it should be possible to withdraw them if the wheels were released from just the top wishbones, the wheels are mounted using a spherical bearing and a top hat threaded bush which pass into the top of the wish bone. These were easy to undo and the wheel could be swung away from the car at quite a sharp angle. But as usual all this does is pull the cv joints apart not withdraw the joints from the diff. At this stage I did notice one of the CV joint boots has a small split in it which probably accounts for all the lithium grease I've been cleaning off, that'll need replacing during reassembly.

The inner CV joint is held into the splines in the diff by a circlip. These are usually really really difficult to get out, because normally when your doing it access is extremely restricted. However in this case I had good access and using a large "Gorrilla Bar" crow bar I applied a little side was pressure between the CV joint and the diff and both joints popped out in seconds. Blimey!



So after a bit of manoeuvring and removal of some six mounting bolts and spacers I had the Diff carrier on the bench (or rather the top of the freezer).

In the picture left the unit is orientated as it is in the car. The front of unit is towards the viewer.


The four mounting lugs at the front are where the engine is mounted onto the diff carrier. Behind them is a starter motor, that provides the reverse gear that the RGB series regulations require. The starter motor drives on the ring gear of a flywheel that is on left of the aluminium chain wheel which, in turn receives it's drive via a bike chain from the engine's output sprocket.

The flywheel also acts as a brake disk, for a Willwood mechanical calliper that provides the handbrake required by the "Must be capable of passing an MOT" part of the regs. The calliper is missing from the photos.

In the centre of the chain wheel and flywheel is the differential, which is an Automatic Torque Biasing unit from Quaiffe. The differential is entirely enclosed and does not run in an oil bath like it would do in a car's diff casing, rather it is lubricated internally by grease.


On either side of the diff are two large aluminium blocks which house the sealed bearings that the output flanges of the diff rotate in. In this side view you can see the silver coloured adjustment plates which are bolted to the aluminium bearing carriers through slots in the diff carrier sides. These adjuster plates can be moved fore an aft by the adjuster bolt on the far left (there's one on each side), and when the chain is correctly tensioned and the chain wheel is in perfect alignment with the output sprocket the pinch bolts are tightened up.

You can also see the splined socket which the drive shaft's inner CV joint fits into.

I needed to remove the flywheel\chainwheel\ diff unit so that I could lube the diff, so I started by removing the pinchbolts and adjusters and I expected the whole unit to drop from the frame, sadly I was wrong and the diff output sockets are actually a little wider then the frame. So using the long threaded rod that is part of the mounting hardware I forced the two side plates slightly apart and out came the diff assembly.

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Here you can see the removed unit, including the bearing carriers. The bearings were a very very tight fit, and rather than badger something by persisting I decided that caution was the better part of valour. I'll ring Tim Pell on Monday for further instructions on dismantling and lubricating the diff.


In the meantime I can degrease and re paint the diff carrier. Although that'll have to be tomorrow. My good lady wife needs to get to the freezer to get tea out :-)