how do I check a diff before fitting

[BMWChris]

My diff is broken (Midget 1500).

I have a spare that came with the car.

How can I check the diff before I fit it? Should I do anything else (clean it etc?)

Should I order some new half shafts while I'm about it? I've got a good spare but at least one has twisted splines. I use the car for competition (as did previous owner) so the get a lot of strain.

Thanks

[john2443]

Check the backlash - slop between input and output sides. Can't remember what it should be but if it's too much there'll be a pause...bump of crown wheel and pinion between power and overrun which may break something on impact.

Halfshafts are a weakness on Spridget axles, yours should have the later ones that are a bit stronger but I would think for racing you should put new uprated ones anyway.

Clean it!? Inside or out. For a raod car I generally wash them out with petrol let them drain and fill up wiht oil, on th egrounds that they don't fail too often and (IMO) it's not worth the effort of a complete rebuild when it may well be OK as is. Whether that's a good enough philospohy for racing though!