I currently have a 10 bolt 3.23 posi (drum brake) in my t/a. I've seen where summit sells 8.5" gears for gm 10 bolts. Will these gears fit the rear that's in my car? If so, does anyone know where I can get some 30 spline axles? BTW I plan on replacing the posi unit along with the gears and axles.

 

No they won't!!!

There where a few 10bolts

yours (87) is a 7 5/8" 10 bolt

The 8.5" 10 bolts came in the mid 80's 442's and GN's and on some wagons and i the 90's they where on the Roadmasters, caprices, impala's etc. They also came on the 70-81 F-body's and so on and so on.

There was also a 7.5" which is in all terms the same as the later 7 5/8"

Also in the mix was a 8.2", but it is rare.

 

Can't explain it any better than that.

There are no 30 spline axles for the 7.5" 10 bolt unless you have a custom carrier and axles made. The carrier just isn't big enough for anyone to make huge axles for that tiny ring and pinion.

28 spline axles are the most you're going to get. 90-92 third gens have 28 spline axles that will fit in any other third gen 10 bolt that is using a 28 spline carrier. Aftermarket 28 spline axles are available from many places that are stronger than the factory 28 spline axles. General cost for the aftermarket axles is around $150 each.

I know www.tomsdifferentials.com has them for $125 each. They're listed for 90-92 but as I just mentioned, install a 28 spline carrier (posi) and use the 28 spline axles in any diff.

I say this because the chance of finding a wrecked 90-92 third gen in the junk yard is low. Not impossible but low because the production numbers were low for those years.

Another option is finding a fourth gen diff. It's also a 7 5/8" 10 bolt, has 28 spline axles and is a direct bolt-in to a third gen. The diff is 2" wider on each side so proper backspace rims are needed.

 

The rear end that I have now is from a 90 camaro, so, does that mean I have 28 spline axles already? My thoughts were whether or not I could put 8.5" gears in the rear end that I currently have. I know the carrier would need to be changed, but is it possible? Thanx

 

No it is not possible. Besides 10 bolts holding the ring to the carrier, and both being chevy rear ends, they have nothing in common and in no way interchange.

 

You might as well be asking if you can use ford 7.5" gears in a chev 7.5" diff. There's more to the diff than just gear size. Parts are not interchangable between different types of diffs.

Your 1990 will have 28 spline axles. Factory axles are not as strong as the aftermarket ones because of how the factory tapers the axles.

Run what you have. Repair/upgrade parts if you ever break something.

 

Hey stephen, you have a big block, maybe you know. I was thinking of putting a 454 stroker crank and pistons in my 305. What do you think. Maybe i need a little machining?