Hiya Nicko
Now I have heard more, Iwould have to agree about it being a final drive related problem.
The symptoms you describe sound to me like the diff pinion gears or the diff side gears. I am not sure how 'mechanical' you are so if you understand how a final drive works scroll to the last line
If not a final drive (mistakenly called a diff by all and sundry
)works as follows:
First of all the main components are the Main pinion (input), the Crown wheel (reduction), the differential carrier and differential gears (allows cornering), and the axles (mongrels of things that break when doing wheelies).
The differential gears are four smaller gears in the very centre of the final drive, two are splined to the axles and known as side pinions and two are attached to the diff carrier by a shaft and are known as diff pinions. All four of these 'pinions' are in constant mesh. So in other words drive comes into the final drive from the propshaft and through the main pinion. The main pinion drives the crown wheel (at a reduction) which is attached to the differential carrier. Because the two diff pinion gears are attached to the diff carrier as well they turn with it (but they can also rotate freely on the shaft). As the diff pinions are in mesh with the side pinions, these are driven as well and because the side pinions are splined to the axles drive is sent to the rear wheels.
But, if one axle is prevented from driving by some external factor then all the drive will take the easiest path and be transfered to the opposite wheel because the whole setup allows the diff pinions to 'walk' around the side pinions as required during cornering.
Soooooooo what I guess I was trying to get at is that if one of the side pinions or one axle was being held or it had a dodgy bearing then a lot of the drive would go to the opposite wheel, hence your wheelspin. The problem you've got is to eliminate all the other external factors like brake shoes on arse about, broken pins or springs and one brake locking on - which you seem to have done.
The only real thing to do is to drop the final drive centre out and have a gecko or perhaps pull that side axle out and check it.
If you have an FE/FC workshop manual the rear axle section has a very nifty exploded view of the final drive so you can see what I was jawing about.
I hope I have helped in some way - good luck.
Nige
