Are all GN 8.5 Posi unit's Auburn's? Are some Eaton?

[Crazed1]

I'm new to all this so I really don't know.
One of my friends is an ASE GM Mechanic.

He told me that some 8.5's came with the Eaton Posi unit,he didn't say wich models or what years.Could be the Trans Am's and Z/28's for all I know.

I am looking for a rear so I want to be able to know what I'm looking at and how much I should be giving up price wise.

 

[Red Regal T]

That would be 2nd generation Z-28s and Trans Ams. Most are 8.5" posi-units, 28 spline. To my knowledge, they are all Eaton. You can only use the posi-unit. The complete rear, drum to drum, doesn't fit. You can find them on here for about $150.

 

[Crazed1]

So I could get an 8.5 from a GN,
then I could install an Eaton Posi from a Trans Am or a Z/28.

Do I have that right?

Will the 3.42 and the 3.73's that came with the T-Type and the GN bolt to the Eaton posi unit from the Trans Am -Z/28?

 

[Red Regal T]

You could install the 8.5 posi, if so equipped, from for example, a 76 TransAm (2nd Gen) into a GN. Just bolt on your ring gear, install with shims in the same position as your "open" unit.

There are 2 series and 3 series posi's. 3 series come with 2.73 gears and numerically higher gears. With one of these, you wouldn't need to use a ring gear spacer (available at Summit). If you purchase a 2 series, then you would need to use this spacer.

 

[Crazed1]

Just the info I needed.
Thanks.

 

[Crazed1]

Are there any newer 30 spline axles that are the same length as the stock 8.5 GN ones?