You’ll need to check the code stamped on the passenger side tube of the rear end to decipher what you have. You might have to use degreaser or lacquer thinner to get to the code.
The stock rear in a 1971 Skylark/GS would be the 8.5 10 bolt. That is not to say that the rear hasn't been changed in the last 46 years. The 8.5 is a good strong rear with great aftermarket support. You can identify it by the corner lugs extending on each lower side of where the cover sits. The rear u joint also attaches with cap screws and metal straps as opposed to u bolts and nuts. The axle code is stamped into the axle tube. If you can find that, it will tell you the original rear gear ratio.
Chances are that you have a 71 non stage 1 GS with an automatic transmission. From Larry's chart the odds are high that you have a 3.08 rear gear ratio which may or may not be a limited slip.
Since it is the 71 8.5”,it could be the 2:73,3:08,3:23,3:42. Is it an automatic or 4-spd? Does it have AC or not? That might help narrow it down.
Hey Larry ... your showing a picture of a GN 10 bolt 8.5...lol. Just messing with you guys... I know it is just for referencing the 8.5 center. 2.93 as Brian stated is NOT a ratio in the skylark for that year. BUT there was a 2.93(14 -41) ratio in the 90's when the station wagons used that ratio so you can get it if you like it...little bit hard to find as it is a discontinued ratio through GM now. I get them from time to time. As I have found most Buicks get the 3.42 or 3.08 depending on the trans and the olds 455 cars got the 3.23 ratios... Do remember that is for off the lot cars... if someone had the car ordered they still could have bought it with any ratio they wanted. MONEY still did the talking back then. Posi track was an option item just have to check your tube suffix code.If it was a true GS with 455 it is likely you have 3.42 with posi trak rear. NOT ABSOLUTE but likely. Jim J D
