7.5 rear suggestions

[SoFloG]

I didn't put a Ford in a gm car. I put a gm engine in a gm car. I've owned all gm vehicle brands and the little factory stickers say "keep your gm car all gm". I will always do that. I caught enough sh*t on another forum for wanting to put a sbc in an 84 4 door delta because it was easier than rebuilding a garbage 307. I could understand if I was restoring a 69 442 or something but come on now.

I'm not trying to "build" this rear, just looking for advice on preserving it and possibly increasing the gear ratio if it was worth it, until I get my hands on an 8.5 or 12 bolt. Thanks guys

 

[SoFloG]

I have an 85 firebird 8.5 with 4.11s available for $300 but according to my little research it would not work without extensive fab work. Is this true?

 

[lilbowtie]

True - 60,s 70.s A bodies can be adapted to fit

 

[olds307 and 403]

What is the difference? Olds and Chevy are not the same, try switching parts between the two. More Ford parts will fit the Olds V8 and back in the day, the 3 SPD manual option was a Ford top loader trans. The early Olds 307 powered big cars better than the 305 of the same era. When Olds went swirl port, smooth operation/mileage was it's only good feature. Through the 70's into the early 80's the Olds V8 was more reliable than Chevy. Until Chevy put half decent valve guides and cams that didn't wear out and go flat in the early 80's, they were not great. Who cares if it is all GM? GM had the wisdom to use the weak 7.5" rear even behind the LT1 and LS1 in the Camaro and Firebird until 2002. I know I bent the Chevy is GM guys out of shape when I put an Olds 350 in my 94 Chevy Z71, the truck could finally get out of it's own way. But it was all GM, so all good.

 

[565bbchevy]

For a street car that you are not trying to hook up with or using slicks I see no issue putting a differential and gear in.
I ran my 7.5 with a Auburn differential and a 373 gear for 6 years behind a 600 horsepower 496 BBC and it never broke and I beat the crap out of it and later sold it for what I put into it when I finally upgraded to a 9" rear.
There is a member on here that twisted his new driveshaft and broke his new trans on a dyno and the 7.5 still survived.

 

[olds307 and 403]

Some people do defy the odds, others have them fail behind stock power. If you do rebuild the 7.5" use the solid pinion spacer and shims, anything to help it hold together. With it, the only reason my pinion failed was because the exploded spider gear chunks got caught between the pinion and gears, bye bye pinion. The Ratec smart sleeve is also supposed to be an improvement over standard crush sleeve.

 

[SoFloG]

For a street car that you are not trying to hook up with or using slicks I see no issue putting a differential and gear in.
I ran my 7.5 with a Auburn differential and a 373 gear for 6 years behind a 600 horsepower 496 BBC and it never broke and I beat the crap out of it and later sold it for what I put into it when I finally upgraded to a 9" rear.
There is a member on here that twisted his new driveshaft and broke his new trans on a dyno and the 7.5 still survived.

Nice! Thanks. I would like to take it to the track eventually but I don't plan on ever running slicks. It's all just until I find some thing better.

 

[565bbchevy]

Nice! Thanks. I would like to take it to the track eventually but I don't plan on ever running slicks. It's all just until I find some thing better.

When I did my 7.5" I could not afford a 9" at that time and I could not find any affordable 8.5" rears either so I decided I wanted to enjoy my car now and the 241 gear open carrier did not work well with my combo so this is the option I went with and have no regrets and will be doing it again for my 86' Regal.

 

[565bbchevy]

I caught enough sh*t on another forum for wanting to put a sbc in an 84 4 door delta because it was easier than rebuilding a garbage 307.

I wouldn't be too concerned about a SBC being your choice for engine, I have personally ruined many Gbody Regal's and Cutlasses by pulling out blown V6's and 260 and 307 V8's etc. and installing built SBC's and BBC's in them.

 

[L92 OLDS]

Some people do defy the odds, others have them fail behind stock power. If you do rebuild the 7.5" use the solid pinion spacer and shims, anything to help it hold together. With it, the only reason my pinion failed was because the exploded spider gear chunks got caught between the pinion and gears, bye bye pinion. The Ratec smart sleeve is also supposed to be an improvement over standard crush sleeve.

Agreed. I defied the odds with an old 82' Cutlass I had back in the day. Never blew up the 7.5 but many do. Here's a look at what can happen. This one was punished by a 6.0L LS engine.