im currently working on putting a 350 (350 horse/400lb ft) and a 700r4 into my malibu. I was wondering if its worth building up the stock 7.5 rear with a posi unit and 3.73 gears or sourcing out an 8.5 from a grand national which i kno can be expensive.
7.5 in rear
- Thread starter malibu78
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If your going to race it every week-end and run slicks it won't last. If your going to build a nice street car and get on here and there at lights and stuff,. It will be fine,but any more hp I would seek out a bigger rear-end.
It's my set up exactly, and for as few times as I break the tires loose, I'm fine with it. When I win the 540 million lottery tomorrow, I'll buy a 9 inch for the car. First thing!
Good axles and a bearing support cover are your friends 
Put good parts in it and you should have no issue with it... I have a stock open high-miler 2.29 behind a 375ish hp/4-speed combo and it's been fine for the couple thousand miles I put on it, but I also don't beat on it (clutch dumps, hard shifts, etc.). If you take care of it, it will last.
Put good parts in it and you should have no issue with it... I have a stock open high-miler 2.29 behind a 375ish hp/4-speed combo and it's been fine for the couple thousand miles I put on it, but I also don't beat on it (clutch dumps, hard shifts, etc.). If you take care of it, it will last.I have a stock 7.5 with 373 gears in my Monte Carlo SS with a 425+hp SBC 406 been working fine for me for years, has a aliminum differential cover with bearings support studs, only use on street no slicks.
IMO, the cost of updating the 7.5 is so close to what a GN rear costs, it's a no-brainer. Go with the 8.5. It''s probably stronger stock than an updated 7.5". I've seen updated 7.5" rears pop on peacefully driven mild V6 automatic cars...
Tommy
Tommy
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