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gmcdermit1
10-29-2010, 01:44 AM
I know this may seem like a silly question but I have a dilemma. I have an 8.5" 10 bolt for my 79 Trans AM but I don't know if I should use it or get a nine inch. I have used the ten bolt for years, literally abused the thing and it held together. I am going to do a fully custom rear suspension and will be cutting the perches off. It is a factory disc brake ten bolt out of a 79 SE Trans AM. I won't be using the brakes so they don't matter.On one hand I hate to cut up a rear end that someone may really need and on the other it works, would be pretty stout with a TA performance cover and some good axle shafts and it's already got a posi. I'm on the low buck thing here. They say a 9" out of a torino or ranchero will work. Also a 1971-2 or 3 Mustang. I need 61.25" overall width to be the same as my stock rear end.Any Auggestions?

big gear head
10-29-2010, 09:17 AM
Even if you got a 9 inch for around $100, you are going to have to spend several hundred dollars rebuilding it with a good limited slip, gears, bearings and other parts. The 9 inch is quite a bit heavier than the 8.5 and it takes more power to turn it. The 8.5 can be built pretty strong with 30 spline Moser axles, Eaton Posi and the T/A Performance cover. I've built many this way and I don't know of any that have broke.

gmcdermit1
10-30-2010, 04:04 AM
All of the things you mentioned will also have to be done to the 10 bolt with the exception of I would probably rebuild the factory posi. Thanks for the input and I also have beat the snot out of ten bolts (8.5") and they take it well. I did find a 9" out of a Torino with the thick tubes and all for $100. It has 3.25 gears, where my 10 bolt has 3.23. I believe I'm going to go this route. After much debate with my buddies! You definately raised some good points but I will have to buy all the parts to rebuild either rear end so I might as well throw it at the 9" which can definately be built stouter and there's more out there. It is also a simpler housing to fab and weld to since it doesn't have the cast center section and I want to run a torque arm.

big gear head
10-30-2010, 07:42 AM
The factory Traction Lock differential in your 8.5 can not be rebuilt. There are no clutches available for it anymore. The only parts that are still available are the cross shaft and the retaining bolt.

The Torino rear end will have 28 spline axles. If you build it I recommend that you upgrade to 31 spline axles.

gmcdermit1
10-30-2010, 02:41 PM
Thanks for the info. I sold the 10 bolt for $300 and scored the 9" for $100 bucks. I don't think I went wrong. I definitely plan on good axles when I get a posi for it but for now it's going to get a redrill so I can bolt the wheels on for mock up!