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gto nut 00 03-28-2006 06:11 PM

I need a step by step idiots guide. lol...
I have a 1983 pontiac grand prix that originally had a v-6 in it. I recently swapped the motor for a 305 sbc. The rear is still the original v-6 rear, and i know it's not going to last long. anyone know how to rebuild so it'll withstand the v-8?


jimfulco 03-28-2006 09:49 PM

It's probably the GM 7.5" unit. I doubt if a 305 would do it much damage unless you really thrash it. I hear the rear end girdles such as the one from TA Performance help them out some.

home brew 03-28-2006 10:18 PM

I need a step by step idiots guide. lol...
All rear axle GM rear wheel drive cars from 1977 to 1990 used the same rear axle. If your 305 is not built up to much the present axle will handle the V8.

This link will give some info on your rear end:

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jimfulco 03-28-2006 11:00 PM

That article only applies to the 7.5" rear ends. GM used 8.5" rears in quite a few post-'77 RWD cars & trucks.

home brew 03-28-2006 11:19 PM

I need a step by step idiots guide. lol...
jimfulco is right GM used a 10 bolt 8.5" rear end as well. Here's a link for some info:

Best Car Insurance | Auto Protection Today | FREE Trade-In Quote

Twistedwrench 03-29-2006 01:12 AM

2 Attachment(s)
Like everyone has said the 7.5 will withstand a 305 just fine as long as it’s respected. There were gm’s born that way 305> 7.5. If the 305 is built up and you are seriously hammering on it. It will grenade. There isn’t much you can do to beef up a 7.5. You can install a better carrier and gears but you are still dealing with a 7.5. If you ever decide to put lower gears in it make sure that you get the 3 series carrier. Do not install the lower gears that are designed to fit a 2 series carrier; they will have a short life. About the only bolt in upgrades for strength will be moving to the 8.5. They are very hard to find and can only be found in these cars. 1984 Hurst/Olds, 1985-1987 Oldsmobile 442, 1984-1985 Hot-Air Turbocharged 3.8L Regals, 1986-1987 Cold-air Turbocharged 3.8L Regals, About a year ago I threw a built 350 in an Oldsmobile Cutlass. I bought a used 7.5 auburn carrier from ebay and a $160.00 new set of Richmond 411 gears. I got two months of playtime before the gears chunked. I was so mad. I now have a $160.00 Richmond ashtray. Having not learned I bought another set, this time used. Same thing chunked again. Yanked the engine back out, sold the car to a kid that was in love with the pile of junk after he saw it doing roasties one day. I do want to say that the 7.5 probably would have lasted a lot longer with someone else behind the wheel. I gave it no respect what so ever.
Picture below is first day out with the car, don’t yea just love that green. And my expensive Richmond ashtray.

gto nut 00 03-29-2006 10:16 AM

Rebuild Rear
Hey guys, thanks a lot for your advice, the motor isn't built up too much, so I guess I shouldn't really have too much of a problem...

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