I know GM cars inside and out covering 50 years, but there are 2 areas I know nothing about, transmission and rear axle internals. 84 Regal has a... 73 Buick 350 mostly stock, turbo 350 with mild shift kit, 7.5 10-bolt posi with 2:29 gears. The rear end is all rebuilt by the previous owner. It's out of another car. (why he chose that route I don't know) I have 2 questions... 1) Will that rear end be able to handle it? I won't be taking it to the strip, I won't be drag racing it, I won't be beating on it. Just a weekend cruiser. But... every so often, a couple times a month, I will be getting on it through 1st and 2nd. Even though it is highly unlikely... there may come a time where hammer it through all 3 gears, but I doubt it. I've heard of V8 conversions blowing 7.5's apart, I don't want it happening to me. 2) If I keep the rear end, can I just change the gears? It's a 2-series carrier. From what I understand I can go to 3.08 max. That would be fine with me. I just want a better street gear than 2.29. I would like 3.08 to 3.42 range. I live in a VERY hilly area, just looking for better suburban driveability. I see they sell custom 3-series gear kits (3.23 / 3.42 / etc) for the 2-series carrier, but from what I understand, it can't be done with the posi unit. I would prefer to keep that rearend, because it's already rebuilt and in the car. I'm hoping that rear end can handle it, and a gear swap would be cheapest and easiest, because cost is a factor. Anyone here a GM rear axle specialist?
The 7.5" rear is very wimpy. And that's being nice. *For comparison sake....the Jeep guys don't seem to have any better results with the Dana 30 (also 7.5"). My brother is on his 3rd or 4th rear in his '88 IROC.....and that only has a TPI 305" w/auto trans. What do you suppose is going to happen with a real engine in front of it?? If you wish to give it a try anyways - I'd at least find a better center section/set of gears. There is an Olds Bravada in my local yard with a 3.42 posi.....I believe they were the 7 5/8" R&P. You can swap those into your housing, from what I'm told. I'd also highly suggest a TA Performance rear end girdle (no matter what rear you decide to use). :Smarty: If you're interested in the 3.42 posi - I can get it for $225. Personally, I'd go with a Ford 8.8" from an Explorer - then put a ladder bar or 4 link setup and coil overs back there. The rears can be found for a reasonable amount and they are between a Chevy 12 bolt(car) and a Dana 60 in strength and size. The Explorer 8.8's come with 31 spline, 1.32" axle Dia., Trac-Loc, good gear ratios are common(3.27, 3.55, 3.73, 4.10), and disc brakes. Tons of aftermarket options available also for Lockers, etc. I don't say all that just because I have a 3.73 8.8 for sale either. They are an extremely beefy rear at a decent price. :TU: Hopefully, our resident experts will chime in.
I have a few parts you might be interested in if you decide to keep the 7.5. Some have good luck with them, some have very poor luck. Email me off list at cacmanjr@aol.com if interested. Thanks!
I would say change the gears first then have an idea on a replacement. I have heard nothing but trouble for the 7.5" rears because they were designed to be in cars with V6 engines and lo-po 5 L. Install the 3.42 gear set and posi. If it blows up, you will know why. For $300, you can get a kit to install the 71-2 Cutlass/Skylark 8.5" rear in your G-body. Now you know why all the TR and GN cars had the 8.5" rears.
As far as the stories I've heard, when people blow up the 7.5, it's because they're still using the stock posi carrier. With an aftermarket carrier, they've lasted into the 10's.
Unless you're neutral dropping the crap out of it, in which you state that you're probably not going to, then the 7.5 will live. In the real world on street tires it'll be fine cause they're just gonna spin. A 175 HP 73' 350 on a 2.29 gear isn't gonna set the world on fire. My 4100lb. 73' 350 Century ran 16.8's with a 3.08 8.5 and your Regal is much lighter which equals not as much heft to propel (I.E. less breakage). Realistically the lower gear set will give you more leverage and thats where the "OOH... HE BLEW IT UP" factor comes in. Along with stickier tires and beatin on it. If you're not going to drag race it but still want more low end for the hills I wouldn't recommend anything lower than 3.08's. Sure you could upgrage the L/S when changing to a lower gear but then I'd be more concerned with that weak 2 1/2 X .065 wall driveshaft twisting. There is always a weak link, the fun part is finding it :TU:
