Jimbo1367

I am in the process of swapping a LS engine into my 70 Camaro RS. Obviously I would prefer a 12bolt, but I will have to settle on a 8.5" with 3.42 posi and need to know what years the 8.5" rearend came in. Any telltale clues would be appricated.

thanks in advance,
Jim

oldtimelt1

iTrader: (1)

71 to81

Isolde

iTrader: (4)

The 8.5 really is 95% as strong as the 12-bolt. Just do 30-splines with matching posi, studs, and a girdle.
Going 33 spline is possible, but that's for putting a 3200 pound big block into the nines.

2nd Gen Fl 'bird

iTrader: (13)

Exactly what they^^^^ said. I've seen one live behind a 9 sec. nitrous car, with trans brake for a LOOOOOOONG time. Also, the Trans Am cars came with the factory posi if you're still in the hunt for one.

Jimbo1367

Thanks guys. I've searched on a parts locater. I found a few 3.42 posi 10 bolts. One on a 77-81 (forgot what year exactly)Z28 and the other is a pontiac.(?) I don't know how to tell if its a 8.5 vs the 8.2 or whatever the OTHER one is. Is there a certian indication externally I can ask the yards to look for?

thanks in advance

MillsMotorvation

The 8.5 that come in 87 Grandnationals have triangle shaped ears on the bottom of the housing, and if it has a trunk sticker the option to the 3.42 posi will be (G80) My 81 TTA came with posi, but it came with 3.08 gear, good luck! I have a friend with a few 3.42 posi units his name is Sam 706-526-8924 tell him Herbert said to call.

2nd Gen Fl 'bird

iTrader: (13)

There is no such 8.2 or "other" in the 2nd gens, Camaro or Firebird. The Pontiac will have the posi unit.(Trans Am that is) They are all the "Corporate 8.5 10 bolt you are after. You can easily add an after market Posi unit down the road if you get one that does not have the posi from the factory. Just to get technical, the '70 Trans Am did have a 12 bolt from the factory, the one and only year. A very rare piece, doubt anyone could find one.

Black&White

Actually the 8.2" was the 10 bolt in the 1970 Camaro. 71-81 has the 8.5". And the 12 bolt was also available on Camaros in 1970. NastyZ28

zamora7

iTrader: (4)

So does that mean that someone swapped the 12 bolt that is now in my 1980 Trans Am?

Jimbo1367

Thanks guys. This is the imfo I was shooting for !!!

dirtplay1975

that would be correct, you got lucky someone helped ya out previously. One thing you have to look out for in the later 70's on trans am's is also that there seems to be alot of them with 2:41 posi's out back so dont assume if its a TA its gonna have good gears.

1970camaroRS

iTrader: (8)

This is correct. I bent the hell out of my origional housing in a sideways slide into a curb years ago. It was an 8.2" that I replaced with a 8.5" out of a '78. Then I rebuilt the 8.2" posi and sold it for a nice profit to a Corvette guy.

8.5" inchers aren't the 'corporate' rear end. When people talk about the 'corporate' rear they are talking about the late model rear which is not an 8.5".

2nd Gen Fl 'bird

iTrader: (13)

Not to start a flame war but, I agree on the 8.2 being in the '70 model. The 8.5 did start showing up that year, just not a high production piece. Starting in '71 it was a "corporate" wide 8.5 10 bolt used in most passenger cars and some trucks, hence the "corporate" name. Very versatile and capable rear. Everyone sreams 12 bolt because it was stronger than the 8.2 in the day. A 8.5 10 bolt is right there with the 12 bolt in strength when built.

Jimbo1367

Thanks. I will start looking real soon(again)