Pontiac Trans Am Rear End?

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Shea Laking

Well-known member
Jan 17, 2009
Colonel Sam's City-Oshawa, Ontario Canada
I have a GM rear end I'm trying to ID... I believe it is out of a late '70's Trans Am, but numbers are kind of confusing...Here's what I've found so far:

on the passenger-side (right) axle tube:
-5P0 161 1

cast into the center section:
- D71
- 1254333
-GM 35

stamped in the ring gear:
-2GM 3984 828 13 40 481

I know by counting teeth on the pinion gear (13 teeth) and ring gear (40 teeth) that I have 3.23:1 ratio. This is also, from what I've found on the internet, indicated by the 13 40 stamped on the ring gear.

Anyhoo, I've tried looking up the numbers on a couple F-body sites www.nastyz28.com as well as www.78ta.com and so far, no joy. It appears that my axle tube stampings are missing a couple of digits!!:confused::(

Does anyone know of any other websites, etc where I could check this out? I'd really like to find out exactly what it is that I have....

Oh, I should also mention that I'm almost 100% positive that this is a TA rearend, due to the shape of the leaf spring mounting plates (they wrap partially down around where the leaf would sit) as well as the fact that it is equipped with disc brakes. The differential appears to be an Eaton Positraction.

Thanks anybody who might offer info or search directions.


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