Will an '88 and up third gen 10 bolt diff bolt right onto an '87 and below third gen body? Reason being is 28 splines. My 10 bolt is showing signs of wear in my '83 and I would like to find a 10 bolt from an '88 and up so I can get the 28 spline axles.

How rare is an LSD found in the newer third gen diffs? My ideal differential would be either 3.42 or 3.73 with an Eaton LSD.

 

Yup; no difference whatsoever externally.

88 & most 89 won't have the better axles. Only a very very very very few 89s, and most 90s, on up.

The LSD that came in 3rd gens was generally Auburn. Never Eaton. The Auburn is GARBAGE. Finding one in working condition is EXCEEDINGLY rare. Odds are, any one you find, is long since wore out, and is completely ineffective. If you REALLY want an Eaton, don't waste your time and effort tracking down a rear with an Auburn in it.

A further issue is the brakes. You DON'T want the 88-back (cast iron caliper) ones. If you have drums now, you will have to change out your master cyl and combo valve to have any hope of them working at all, and at best, they're still pretty pitiful. The ones to get are the 89-up PBR (aluminum caliper) ones.

It is almost vanishingly unlikely that you'll find a used rear that's (1) 28-spline, (2) 3 series, (3) posi, and (4) has the good brakes. Seems like most people, myself included, have to build that combo themselves.

Another approach would be to find a 98-02 (LS1) rear. Those have a MUCH better LSD, better brakes, bigger axles, and better gears to begin with. Only down side is, they're about 1-5/8" wider on each side, which means you need to change to 4th gen or Vette wheels to get the correct backspacing. Which if you're buying wheels anyway, isn't a big deal.

 

You may find the following info useful at some point:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

Sounds like I would be better off just replacing the internals and going 28 spline, Eaton LSD.