I have a 1986 Trans - Am with a 1975 chevy 350 with the TH350 Trans.Which rear -end do you guys recommend.Thanks

 

Unless you buy an aftermarket direct replacement differential, you're stuck with using a factory diff from any other 3rd gen. A 4th gen diff will fit but it's about 2" wider on each size. There's no real strength difference between a 3rd gen and a 4th gen diff.

 

89-92 Rears had PBR discs instead of Delco/Moraine discs. These are preferred.
90-92 Rears had 28 spline axles rather than 26 spline. Also preferred.
98-02 Rears from an LS1 car had a Zexel Torsen posi. This can be swapped to any 28 spline 7.5 or 7.625" ten bolt.

Some people think the 9-bolt is stronger than the ten, I belong to the school that I'd like to be able to repair it if it breaks. Which with the nine bolt is VERY expensive. Parts all come from Australia. Some nine bolts have PBR brakes.

Oh, and if you get SUPER lucky, Gm Performance offered a Dana 44 for these cars. It's the ultimate "stock" rear.

Other options are a Strange Engineering Dana 60 or GM 12 Bolt, a Moser GM 12 or 9" Ford, or a Currie 9" Ford. Moser uses threaded torque arm mount holes on their rear ends, and the bolts can get loose and cause some nasty damage. It might not be hard to get under there once in a while and tighten them, but you shouldn't have to do it.

In order of least to most strength:
82-02 GM 10 bolt from a Camaro/Firebird (7.5/7.625" ring gear)
85-89 GM 9 bolt from a Camaro/Firebird (7.75")
GM Dana 44 from GMPP (You may never see one. Rare.) (8.5")
GM 12 Bolt Aftermarket (8.75")
Ford 9" Aftermarket
Dana 60 Aftermarket (9.75")

Strength is weight. The twelve bolt is the lightest aftermarket, and the Dana is the heaviest. I believe the Dana is 20-30 pounds heavier than the Ford, and the pinion contacts the ring gear at an angle that leeches less power from your drivetrain. It's more efficient than the 12 bolt, which is about 1% more efficient than your 10 bolt, which is 5% more efficient than the 9".

And I think that's all I know.

 

thanks for all your help.I'm Thinking about just buying 3.73 gears for my rear and call it a day.

 

About how much horsepower can those rear ends handle? I need one that will handle probably around 400 at the flywheel, but a little insurance would be great too.

 

What would you do to get the 3.73 gears. What would you have to buy and would you be able to keep the rear? I have an 1986 Trans Am

 

V6's have broken them on the street and big blocks have pushed them into the low 11's on the dragstrip. There's only so much you can do to make them stronger but the tiny ring and pinion will always be the weak link.

 

400 flywheel you'd do fine with a slightly built ten bolt. See if you can get the diff out of a 98-02 Camaro/Firebird with the LS1, swap that in. Buy some good quality gears in the ratio you want, and a decent set of axles. Shouldn't have to worry about it. There's an article in the tech section of the site about beefing up the 10 bolt.

 

Richmond gears makes a good set on gears