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-   -   GM Posi ? (

77 Monte 01-25-2006 10:02 PM

GM Posi ?
I'm gonna upgrade from an open to a Posi or Limited Slip. I have my eye on a GM 8.5 " 10 bolt 28 spline for sale on Ebay. My 355 is basicly a 1970 LT1 pushing about 320 HP. The gear ratio is 3.73 The car will be used 90% for street use. Can I get buy with this GM posi or should I set my sites higher?

Centerline 01-26-2006 07:17 AM

GM makes pretty good posi units. I would think you'll be fine but keep in mind that anything used is probably going to need to be rebuilt first.

TORI1 01-26-2006 10:23 AM

10 bolt 8-1/2" 28 spline
I've got a Gm 10 bolt 28 spline 8-1/2" locker for sale for 100 bucks..

71C10 01-26-2006 11:56 AM

I replaced my GM Eaton style with a Detroit Truetrac:

Awesome unit for a street car, very smooth power transfer, no clutches, no cones, no ratcheting and no limited slip fluid!

jimfulco 01-27-2006 03:27 AM

Check the casting number on the unit to see if it's compatible with your gears. If it says 410409, it's a 2-series, and won't work with 3.73's. If it says 410408, it's a 3-series, and should work fine.

TORI1 01-27-2006 07:13 AM

Series 2 Or 3
It says neither 410409 or 410408

the ONLY numbers on it are as follows:
(all are on the opposite side of where the ring gear would be (i guess passenger side of the carrier))

in large cast numbers appears 04-6
in smaller cast numbers appears both 8Y, and 18D (maybe 8D)
and in stamped numbers appears E61 E61A

no other numbers appear on the entire carrier

what do you think I have??? eaton??? GM??? series 2 or 3 ????

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