[1FST4DR]

Hey its Tim here, i have a 1981 Pontiac Grand LeMans, i originally bought it from a guy who told me it has a 350 and a posi with gears, turned out it was a 305 and no posi, it does have 3 73 or so gears in it(had to figure it out myself), he told me they were out of a camaro ( not sure what year)...is this possible or is this guy just brain dead? ive also seen on here people are talking about 8.2 and 8.5 rear ends. what do these numbers refer to and which would my car likely have? is there somewhere i can check? sorry about all the questions but im thirsty for knowledge... also what kind of car could i get a posi unit from that would directly bolt into my car? any info would be greatly appreciated, thx alot...Tim

[scholman]

Tim,

The numbers you are referring to have to do with the diameter of the ring gear. I have run into this problem on my 1976 GMC Sprint. I took out the original rear end and put the rear end from a 1974 El Camino. I have tried to buy all the bearing for the '74 but was told without having the bearings "in hand" there are too many choices.

Good Luck
Scholman

[home brew]

This is a good reference guide to rear ends. It will explain the differences.
Try using the search engine to read some posts about Chevy rear ends and see if anything there matches with what you have. If you can't find anything eventually someone here will get back to you. I don't think with the info you have given so far it will be easy to help you.

[oldsmo]

An 81 LeMans is like an 81 Malibu right?? I would have to say 7.5??

[1FST4DR]

yah my grand lemans is basically a malibu, i didnt know there were so many choices of bearings and ring sizes and stuff, if only everything were universal, whys everybody gotta be different? anyways, i guess ill look into a malibu posi, or try and find out if any car came with a stock posi that would work for my application, thx guys PS that is one sexy *** monte you got there oldsmo

[fast68]

7.5" unless itsa GN or turbo regal or 9C1 or 9C6 or something else special like that

good luck

[oldsmo]

Originally Posted by 1FST4DR

PS that is one sexy *** Monte you got there oldsmo

I wish that was my Monte. That is my friends car I cleaned up the motor bay and dropped in the crate motor and electrical fan and other things. That car is incredibly clean, the pics I have don't do justice. He spent allot for that car. I like the fact that you have a Pontiac LaMans(g-body), don't see them at all. Keep that thing clean there is allot of Pontiac guys that probably woudn't mind getting there hands on that. making some mods and putting in a 455 done up with I tranny and rear(8.5) to take the abuse would be absolutely ****ing sweet.

[1FST4DR]

Yeah i love my G-Body, once i figure out how to work this stupid scanner, ill post some pics of my 81 Grand LeMans 2 door...R.I.P. .....dark blue, blacked out windows, 355 ....anyways....so im guessing that my rear end is a 7.5 since a few of you have said that, does this mean its a 10 bolt?? is it possible to get a ring and pinion set out of something else thats a 7.5 and just bolt it up?

[oldsmo]

which does it look like?

[1FST4DR]

hey oldsmo, im pretty sure its the one on the left with the little nubs on it, i havent seen my rear end for a while because my cars been sitting in my dads garage awaiting a motor transplant...starting today though..cant wait to hear that gear drive...anyways, ill double check on the rear end thing but im pretty sure its the left one, what does this mean? also is there a gasket that goes on the diff cover or do you just use black rtv silicone or something along those lines? ive never looked inside the rear end of my own cars but i think im going to change the fluid in there real soon...thanks again, Tim

[oldsmo]

The one on the left is a 7.5 - and the other is 8.5

There is gaskets for that but most people I know just RTV it.