info needed on g80 posi in generel on 91-96 GM sedans/wagons

so to start off i have a 77 Cadillac fleetwood, its my project car. and the rear end on a Cadillac from that era has little to no aftermarket parts and im looking to have a posi in it somehow. Ive been told to just look for a posi out of 77-96 gm anything 10 bolt cause it will be a direct bolt in to my 77 caddy. so i came across a 91 or 92 Oldsmobile custom cruiser wagon, looked at the rear end and to my luck its has the posi tag on it. BUT after taking the rear end home i realized i forgot to look for the options codes and whatnot printed on the sticker where ever it was put on wagons back then to see any info about the rear end.

so what i want to know is, the rear end i got from that olds wagon, is it a g80 posi? more to the question when it comes to posi and limited slip differentials in general, are they all basically just a g80 nothing else? like for example an olds wagon to a caprice or to a Buick road master or any full sized gm sedan/wagon 91-96, g80 is the only type of posi they had for an option? i would also like to know what gear ratios were offered as well if anyone knows. anything around a 3.08 and my 472ci wont complain much.

as far as 77-96 anything 10 bolt the wagon rear is longer then a sedan rear. i think it is 3'' longer so check that. the gearing could be a 3.23 that was a option. but if you want to be sure open the rear up drain fluid and count the # of teeth onthe pinion and on the ring gear divide the # of teeth on the ring by the # on the pinion that will tell you the gear ratio. if u dont want to open it up mark the yoke and turn the axel one full turn and count how many times the yoke gos around . if it goes around 3 and a 1\4 turns it would be 3.23. if it is a 256 rear and you want to reuse the center and plan on steeper gears you will need to use a spacer or after market gears that are for use on a 2series carrier. as far as posi open it up and look at the center section look for clutches and a big stamped metal spring in center. if u post a pic of center i could tell if it is a posi. oh some 8.5 posi rears use a gov-lock posi they are pretty weak and i would avoid them i never seen on in a b body yet

from what i looked up the wagon is 3 inches wider then my caddy, not sure for this type of swap if i have to shorten the rear to get it to fit properly in the caddy. but my car has the optional disk break in the rear and the olds rear i got has drums, making into a disk set up might shorten it a bit? im not sure. at least its not to short to use. before i do anything im sand blasting the crust stuff off before i open it up, it sat for how long half in the mud. it will be easier to go back to the the junked wagon and look for that code sticker, if its still readable ill go by that, if not ill defiantly do what is suggested and open it up and count the gears, have to change out the old oil anyhow.

Quote :

Ive been told to just look for a posi out of 77-96 gm anything 10 bolt cause it will be a direct bolt in to my 77 caddy.

It's not. The 77-81 Cadillac rear end is a 12 bolt internally, with a ten bolt cover. Corporate ten bolt posis do NOT fit. There is a factory posi for the 77-81, it's rare to find. Head over to the RWD section of cadillacforums.com/forums and you'll learn lots more.

i did find the vin number stamped on the olds/Chevy 10 bolt axle it says

4 h
26015047

hopefully when i go back and look for the code sticker on the wagon ill find out what i need to know