Ball diff's
 

Having a nightmare with the rear diff on my Cat 2000, I either have to run it fully tightened because as soon as I loosen it is too loose. If I race with them fully tightened up and I going to cause any damage?

Also why would they been working loose? I am guessing the ball bearing are old (new ones on order from a bearing specialist) its a nightmare with Schumacher not manufacturing parts.

I must have rebuilt this diff about 5 times always with the same problem

Just a quick thought with regards to the diff coming loose, have you checked the diff screw/nut for any wear/damage? And also have you checked the four spring washers which hold weight on the diff screw are fitted correctly and also still hold there shape. If the spring washers are compressed flat then there will be no tension on the diff screw causing the diff assembly to become loose?

I doupt the diff balls would be causing the fault. The diff balls usually wear over time or gain flat spots which it turn causes the diff action to become less smooth.

yeah think the washers might be the cause, gonna have a search of the net to see if I can find replacement ones. Bit of a nightmare running a vintage car.

I would say its the Plastic part (u1887 if blade driveshafts) that has lost its thread that the diff screw goes into or the m3 nut in it if its the plastic driveshafts version. Might even be the wrong length screw as two different types.

Also make sure the screw head is on the LHS of the car.

definatly the concave spring washers have collapsed giving no pre load, making it hard to adjust