Rear End Questions

[hurst1979olds]

I have a 79 Cutlass H/O. I have a 500hp stroker small block oldsmobile engine. I have a built th350 trans with a 2800-3000rpm stall converter. I'm looking to upgrade to either a 3.42 or a 3.73 gear and have NO plans to put a overdrive trans in. I do drive this but most of my travel is under 55mph and I will be taking it to the track. Let me know your opinions and experiences.

My other questions is I have a 3.08 gear in the back. The car was suppose to come with a 2.73. So when looking for ring gear sets they have 2 different once for the 7.5 rear. They have a gear set for a 3.23 and higher carrier and a 3.08 and lower carrier. Is ther casting numbers on the carrier that I can look up to find out which one it is. Then looking at installation kits for the 7.5 it seams they only offer the complete kit with bearing and everything for 1982-1998 rears. How do I find out what year rear I have. Obviously someone has changed out my rear or just changed the gears. Any info would be greatly appriciated.

 

[JBreu]

I would think someone only changed the gears and not the rear end...Seems like way too much to swap out a 7.5 rear =for another 7.5 rear............If you did buy gears for a 2 series carrier and actually have a 3 series one..You can buy a spacer or return them and get the correct ones...But IMO here, with that 500 HP your making you will blow that rear end up..You oughta try and save up the $$$ and go with a 8.5 rear, 12 bolt rear or even a 9" rear.... 8)

 

[dogsht]

Stoker small block Olds is usually 380ci. Much like a 500HP chevy 383 it would make lots of torque not need real low gearing and as Breu said be hell on a 7.5. Anyway with slicks or drag radials and some suspension work it sure would. My guess is you bought this car as a stroker Olds build would not be for the novice. Aside from a 7.5, 8.5, 9" choice for this car I would say some 3.42 or even 3.73 with a tall tire would work well for how you plan to use this car. That said this car might not be all that much quicker with that gear change or any at all if you are on street tires and it goes up in smoke. Things to think about.

 

[tlcjr88]

jegs will be your best friend call them at about mid night thats when the people are more helpful 1 800 345 4545

 

[custom442]

If you are taking this to the track and will beat on it, the 7.5 won't do. It can handle it, but not reliably and not for a long time. Though there are 7.5" out there that launch with slicks and about as much power as you. This is usually on newer 10 bolts not the older g body ones. At least an 8.5/8.625 if not a 12 bolt. 12 bolt or 9" is the best route. 14 bolt 5 lugs came in 454 ss trucks if you can find one...all these three will require fabrication and welding unless you get one of the housing kits for 700-1000$ from different places

The 7.5" to 7.625" used larger ring gears (1986). 1989-1990 moved from 26 spline to 28 spline.
(similar but not, to when GM upgraded the 8.5" to 8.625" in 1999-2000, those used different carrier bearings)

Dogshit is correct, I have 2.14's and can't get traction at 2500-3000 rpm in second gear with a th350 and stock tires. If it had very good tires in 1st gear it would be similar. So 3.73's would be useless on the street.

...I think the stock g body 3.08's came with the towing package? Not for sure, this could be misinformation

 

[hurst1979olds]

I had bought the car and someone took out the Olds 350 and put in a 1967 330 Olds. The trans was a 1977 th350. But I got a different th350 in there now. So someone had done some work to the car and I was thinking maybe the rear was changed. Looking at it it doesn't look new and the couple times I had the cover off it didn't look like it was touched. The posi is nice and tight too. The motor I have in it now is a 434 Oldsmobile stroker small block.

 

[midwestls]

I wouldn't spend any time or money on a 7.5 when your making that kind of power. Look around your local race tracks. From past experiance I know alot of the guys that run (gulp, then the tears start...) G Bodys, use ford 9"ers. Usually you can find someone that already has an extra one fabbed up for a G for pretty cheap. And once you have the houseing parts are endless and relatively inexpensive. Thats where I got mine. Just something to think about.

 

[MD13ailey]

I raced my car with a mild small block on the ten bolt with a mini spool. It didnt actually break but when I swapped it for the 9" it was getting ready to come undone. Dependin on how much you wanna dig around in the wreckin yards, you could buy the 9" housing from Quick Performance $365 + axles or $745 with everything but a center section (I got mine from the 9" factory). Then go to a wreckin yard and grab a 9" center section out of a half ton for truck, bronco, an some cars. I got the disk brakes off a continental 11" rotors and such and they do fit with a 15" wheel I'm running vette ralleys. I'm currently running the 9" with 28 spline axles a spool and 4.10 gears on 29x9 toyo slicks havent had any problems. I'm making about 450hp and it runs 12.20s at 110mph. I'm gonna upgrade to 33 spline axles and such for my stroker which will hopefully be goin in after I get taxes back. I drive it on the street occasionally and I drive it to the track about 25miles away