View Full Version : OK what size rear end do we have???

09-03-2010, 01:26 PM
I have a 01 Trans Am with an auto trans and 3.23 gears and a torsen, all stock. So I called Summit looking for spool and they said I have a 7 5/8" rear with a 28 spline. Then I called Jeg`s and they said that I have a 7 1/2" rear with a 26 spline. Who`s right? What is the spline? Does anybody make a good spool that will bolt right in? I want her to hook like a cat on carpet and no I don`t have the money for a 12 bolt. Thanks!

09-03-2010, 01:35 PM
the ring gear is 7.625" and has 28 spline axles, they DO NOT make a spool for a 10 bolt. You need to upgrade.

09-03-2010, 02:11 PM
So does that mean its a 7 5/8" rear end? Who makes the best posi for a 10 bolt?

09-03-2010, 03:05 PM
you've got it, as far as the best posi I have no idea. A detroit locker is probably the strongest thing you'll find but I wouldn't recommend spending a dime on a stock 10 bolt. Find a stock diff for cheap if you need to drive the car and run with it.

09-03-2010, 04:42 PM
our OEM parts are 10 bolt 7 5/8" ring gear on a carrier that has 28 splines.
a 10 bolt 7 1/2" 28 spline carrier is completely interchangable with ours as there is no carrier that is designated 7 5/8" 28 spline,GM used the 10 bolt 7 1/2" carrier (whether it be Eaton,Auburn,or Torsen) in our rearends. a 10 bolt 7 5/8" carrier is a 10 bolt 7 1/2" carrier. the 7 5/8" designation comes from the ring gear. aftermarket ring gears(sets) of 3.73,4.10, & 4.56 for our cars are 7 1/2".
ring gear sets from S10 trucks and S10 blazers are 7 1/2" and are interchangable into ours,some(those that are 26 spline are not) of the carriers are also interchangable.

09-03-2010, 07:24 PM
OK thanks, now I understand. GM is cheap! LOL

09-04-2010, 02:08 PM
Really wasn't a matter of being cheap,they had to stay cost/price competitive with the Mustang.
It's the same(basically) rearend used for 2 generations of f-bods.
Adapting/modifying 8.2" 10 bolts,8.5" 10 bolts,& 8.8" 12 bolts to accommodate the f-body platform as the power increased as the years progressed would have added too much $$$ and possibly started losing sales.
For example,the 98-02 LS series is perfectly suited for as GM intended for the typical/average buyer.It wasn't intended(from GM's point of view) for high horsepower engine mods,6000 rpm clutch dumps,sticky drag tires,and so on.
Go away from the drag racing realm over to the road racing/autocross realm and they don't do a lot of complaining about the rear because they don't subject it to the abuse of dragracing.Some suspension mods and tuning and you get a excellent handling track car.
You wanna start using it way beyond its' intended purpose,start expecting to pay for stuff to handle what you want to do.