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10 bolt GM Rear End Rebuild

15K views 9 replies 4 participants last post by  big gear head 
#1 ·
I picked up a cheap 10 bolt GM rear with the series 2 carrier & 2.56 gears. I don't want to spend the money on a new differential, but just an open carrier, swap out the parts and install a set of 3.73 gears. I've done gear swaps before without problems, but never messed much with the differentials. The clutches look OK but I'm not an expert on this. They still have most of the swirl patterns in them though and the spider gears look fine.

I can't find too much on the internet as far as doing this work. Is there any clearances I need to be concerned with? I see there are shims behind the clutches.

The rear is going in a 56 Chevy pickup with a GM crate motor & 200r4, primarily to be used for street cruising.

Thanks,
Ken
 
#3 ·
I was planning on purchasing a series 3 bare carrier case & using my internal posi parts from the series 2 case so I get the gears I want. The Powertrax system looks nice but is almost as expensive as an Eaton or Auburn setup, but I don't think I need that much in the rear for my setup. A stock posi should be fine.
 
#8 ·
The 3 series case that Summit has is going to be a standard differential case. What you have in the Trans Am rear end is a Traction Lock differential, which is a limited slip (posi) differential. The parts in the TL will not fit in the standard differential case. There are no slots for the tabs on the clutch plates and there will not be enough room in the case for the clutches. The TL cases are no longer being produced. You will have to find a used 3 series case with the casting number 410408 (your 2 series will be 410409) to use your internal parts. If you can find a 3 series TL with broken gears then you will have what you need.

The clutches need to be shimmed for the correct preload. The problem with the TL is that there are no shims sets made for it. The TL was assembled with select spacers behind each clutch set. I have found shims that will work in the TL, but they are not available in a set and the individual shims are not cheap.

You might be better off with a new Eaton 3 series posi or a Duragrip 3 series. If you would like more information on the Duragrip send me an email.

Ring gear spacers cause a number of problems and I always try to discourage their use. Here is what I posted on another web sight.

OK guys, here is my experience with ring gear spacers. Click on the pictures for a better view.

First is the rear end with all of the ring gear bolts broke off. I have rebuilt many rear ends like this, but most of the time there are only about half of the bolts broke. This one broke all of them and the ring gear was spinning around the posi case and the car wouldn't move. This happened at a very slow speed, so no other damage was done. If it had been at a higher speed the rear end could have locked up and cause more damage.


The next 2 pictures are of a 2 series differential for the 7.5 10 bolt. Notice in the first picture that the machined area that centers the ring gear on the differential is wide and there is plenty of area for the ring gear to contact. The ring gear usually is a press fit on this area. In the second picture there is a ring gear spacer on the differential. Notice that the area that centers the ring geaer is now almost completely gone. There is a chamfer on the ring gear that was as large as the remaining area, so when the ring gear was placed on this differential with the spacer the ring gear would move around with nothing to center it. This can cause rapid gear wear and possible bolt failure.
 
#9 · (Edited)
Thanks for the information Big gear head, very helpful. Now that I know more about differentials, (open meaning non-posi not empty case!) it looks like I will need to buy an aftermarket unit like the Eaton. What's the difference with the Powertrax, this mounts in an open carrier? Looks like it's different than a clutch style posi.
 
#10 ·
The Lock Right works like a Detroit Locker. They work well and they are easy to install, but the pop and jerk a little sometimes. Not a big deal, but some people don't like it. They install in a standard differential case.

The Eaton Posi is probably the best street/strip differential for most GM cars in my opinion. They are rebuildable, but usually don't wear out. There is also the Duragrip, which is a copy of the Eaton with different clutch material for about $65 less.
 
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