Rear end Options? stock 7.5? 8.5? ford 8.8?

[thedoctorisin]

1979 olds cutlass...
I just did an LT1 swap and now to get the full potential of the power i need to look into my rear end. now I've got a 7.5 with 2.23's. i was thinking about trying to find maybe something around 3.55 or so. but is there any GM vehicles that share the same carrier specs? like could i pull parts out of a posi IROC or something like that?

I know the GN 8.5's are the thing to get/have but most of the time they will run you 1000 buck or more unless you have a sweet hookup or are so lucky to find one in a yard.

I've herd of guys building ford 9 inchers... seen them for sale already built on ebay... still a 1000 tho.

the one i was leaning towards was a ford 8.8 out of maybe a lincoln or explorer or something of that nature, I here some came stock with LSD or posi.

budget build is the name of my game so cheaper is better. I can weld so modding up another diff doesnt scare me but if there are more subtleties to it than cutting off the old and welding on the G body fixtures keep me posted.

 

[nycutlass]

i would do the ford 9" and never have to worry about it again .

 

[DRIVEN]

Explore 8.8s are 59.5" wide. Pretty close to a Gbody. The '95-up have disc brakes and many have limited slip. Ratios are 3.55, 3.73, and 4.10.

 

[thedoctorisin]

what would i have to mod if anything to get the drive shaft to mate to the diff properly?... this will probobly be my route unless i can Salvage Iroc 7.5 parts.

 

[DRIVEN]

The pinion flange is flat on the Ford so you'll need to fab a driveline. Don't forget that the wheel bolt pattern will be different too. No such thing as an easy bolt-in :lol: . This one is upside-down:

 

[thedoctorisin]

I went with a posi unit out of an 84' Trans Am. Direct bolt in minus the shims.

 

[80_cutlass]

8.8 ford rears are pretty strong and plentiful in the junkyards and come with decent gears as is. The guy I buy parts from feels the 8.8 is a better rear than the fabled 9 inch. He's been building rear ends for race cars and mud trucks for about 30 years....I put a narrowed 8.8 behind a 400 Dodge in a 74 dart, and its still going strong.

sb

 

[JBreu]

I would just go ahead and grab a 12 bolt rear from a 66-72 era A Body car and be done with it....These are just as strong as the ford 9" and the Dana rears.........Super Chevy did a test /comparison on all three a few months back........Keep your GM car GM JMO 😀

 

[thedoctorisin]

the 66-72 A-body's are pretty close to a direct fit as well aren't they? Any links to any swaps on here I'll check em' out?

I haven't had a chance to go out and beat on my 10 bolt since I did the posi swap but i'm having some driving issues with my LT1 i put in it. revs and idles fine but when its in drive or you try and do a brake stand it just sputters. still drives well and i can get into it a little bit without it bogging down. it may be a bad fuel regulator or my pump isn't strong enough... I'll be pissed if its the fuel pump though... brand new.

 

[lostsheep]

12 bolt is basically a direct swap. you just need to buy converion upper control arms from edelbrock. i think its 1" wider on each side but these g-bodies need it lol. IMO the stock diffs were to narrow