[vertigto]

So my 70 GTO is a peg leg with factory 3.23 gears (which I think will be fine for a mildly rebuilt 400 A/C car). Would like to make it a posi...what are the best options out there?

Ironically, I just got a price drop email from Jegs on an Auburn differential for $339 (+ $10 off promo).

https://www.jegs.com/i/Auburn-Gear/1...&submodel=BASE

[mrennie]

This could be fairly easy...if you will use the same gears, measure the existing backlash of the gears, then replace the carrier with the limited slip carrier of your choice and adjust side shims to get proper preload and same backlash as before.

FYI, Auburn carriers are usually cone style and while cheaper, are not rebuildable. Eaton clutch style is the gold standard.

[mgarblik]

Based on your description of your engine and goals, this little limited slip unit would be a good choice. With street tires, it should get the job done. Inexpensive and a pretty strong warranty. As mentioned, not rebuildable. The cones bite directly into the case. So in real high powered applications, they can damage the case and then the entire thing is a throw away. Doesn't sound like you would overpower it with your description of the 400 engine as mild.

[70gtojosh]

I put the auburn #5420114 in my '70. I had to enlarge the ring gear bolt holes to accept the original 3.23 ring gear bolts. Think the new auburn unit ring gear bolt holes were 3/8 and I had to open them up to 7/16. I wanted to keep the 3.23 ratio. I could not find anyone who made a 3.23 gear new.(which was ok in my situation, the gear was ok) by drilling out to 7/16 you may limit yourself to the ratios you may want to try. I could find a 3.08 and 3.36 ratio and I would guess they were made with 3/8 bolt holes.

[FrankieT/A]

Back to the OP's question, The Auburn would work for you, but as commented before it is not rebuildable and not the strongest out there. Low performance would be ok. But for the labor involved I would step up to the Eaton for about the $150-170 more.

[vertigto]

Sounds like this is what I should consider...

https://www.jegs.com/i/Eaton/362/196...&submodel=BASE

$492 is reasonable. I'm shooting for 400hp, but you never know.

One review/comment is of concern...although 4 years ago.

"Close inspection of the Eaton posi revealed apparent casting flaws in the tooth root line of one of the side gears at the heel. Eaton advised not to use. Currently the posi is being exchanged for another unit. Good response from both Eaton and Jegs to resolve this problem."

Gotta imagine they've resolved by now, but has anyone had a similar experience?