on the 88 formula with 4 wheel disk brakes, it's a factory posi unit.

does any 10 bolt gasket fit?
http://store.summitracing.com/defaul...=KeywordSearch

and can i use a 10 bolt rear end cover or girdle?
cover like this?
http://store.summitracing.com/defaul...=KeywordSearch

or do i need one for an 8.2" 10bolt diff?

can i use this fluid with 75-90 synthetic gear oil?
http://store.summitracing.com/defaul...=KeywordSearch

there is a posi additive that needs to be used correct?

http://store.summitracing.com/defaul...=KeywordSearch

I want to change the gear oil and add synthetic gear oil

 

1. No.... only ones for a 7½", or 7-5/8" 10 bolt. So for example the ones for 8.2" (60s) and 8.5" 10-bolt won't fit.

2. No. That's for a 8½" 10-bolt. Besides, it's nothing but monkey-spank, it's just a regular plain old nothing cover with chrome slapped on so that it will show up the rust better. What you really want is something like this http://store.summitracing.com/partde...SME%2D8510400, or this http://www.taperformance.com/gm.htm for the 7½". Those actually do something useful besides keep the fluid from falling out.

3. No. Not the 8.2". That was discontinued in about 70 or 71. You have a 7½".

4. Yes.

5. Yes. You will only need that if you actually have posi, which you won't really know for sure until you take the cover off.

 

ok thanks for the info

wasn't sure if they were 8.5" rear gears in there.

if i bought a rear diff cover i'd consider the TA performance type since they add some support.

it has a posi unit according to the build code, and the fact i jacked it up, both wheels spin the same direction and it has the extra tag on the rear, plus it doesn't look like it was touched before.