My stage 1 came with a posi rear end (maybe) but only one wheel turns when i pounce on it. Jacked it up and wheels turn in opposite direction when i spin by hand. So its a limited slip. Which apparently is a posi? Anyway, what would cause only one wheel to spin on a limited slip? I thought after a certain amount of traction was lost the other side kicked in which isnt happening. i know nothing about rear ends, what should i do? o No:
yes and no . you have what is known as an open carrier . limited slip and positraction are termology gm used for their positive locking differential . as each mfg called it by a different name . with a posi there are clutches , either mechanical or frictional to allow more torque to be delivered to both axles , in theory equal .yet still differate around turns when the inner wheel needs to turn less then the outside . where if you jack up both wheels off the ground and turn one , both wheels will turn the same direction
Sounds like it's not a posi to me. If your car came with a posi originally, maybe it's been replaced sometime through the years?
posi yup,its either a trashed limited slip or an open rear.the way i understand it a "true"posi has both wheels spinning the same at all times.race only,wouldnt be safe on the street.also called a detroit locker,cause both axles are mated in the carrier,and are locked.a couple of my jeep buddys have them and are great for traction,but scary as hell if you arent going straight :shock: limited slip has clutches that transfer traction to the spinning tire,what most muscle cars have.open or "peg leg"where only the right side has drive.
Detroit Lockers..... can be fun in some circumstances. Had one in the 70's in a Mach 1. It made some rather unsual clunks and bangs during acceleration, scared a few older citizens into thinking my car was about to fall apart. Then I'd mash the go pedal, and see ya later. :bglasses: Going around corners, I'd usually step on clutch to minimize the ratcheting action. I'd gladly take another one of those in any stick shift car. :TU:
You apparently have an open differential. The tires should turn in the SAME direction if you had a limited slip. Keep in mind that "Positraction" is GM lingo for a limited slip diff. Ford uses "Traction Lock" and Mopar uses "Sure Grip" for their limited slip units. Even if it is loose, the tires should turn in the same direction with the car jacked up, as there is little bind in the rear under those conditions. You might consider a Power Trax type unit for a budget locker. I put one of those in my GN 8.5 open carrier in about 2 hours. It just replaces the spider gears in the open carrier. Thanks, Rudy E.
hey guys, I dont know really much about rear diff. too.I got a Skylark custom clone into a GS455 (455, TH400).I didnt know what gear I had, so with my brother I counted approximatly 3 1/2 turn of drivin shaft for 1 turn of wheel!Which would be a 3.42?! Were those available on a Skylark Custom in 1970??And, when I do a burnout, both wheels always turn ( like a posi, (limited slip) ) and when the car is jack up, the wheels turn on different side ( like an open carrier (regular) ), whats up with that??!!! is it a limited slip???I mean , every time a do a burn out, or when I punch it, both wheel turn....
Differentials You guys that are unsure about your carriers (open or posi) , Just jack up the car and take that cover off. It will not mess anything up. You probably all need to change the fluid anyway. Then you can absolutely tell what you have in the housing including the gear ratio. Cost you some time , fluid and a Gasket. But you will know and see if everything is good. If you are unsure about it even after opening it...Just shoot some pictures and we all will help you ID it. Ok? Good luck, Jim
There should be a code on the right side of the axle shaft that can ID the axle. I agree, to open up the rear and change the fluid. You will see what kind of shape the rear is in.
Marc, Many cars that were sold new here came with the posi rear axle because of the road conditions in winter. And the performance axle was also available so it's possible that you have it in your Skylark too (I don't know all the ratios that were offered in 1970 but 3.42 axles were). I had a 3.42 posi in my 1968 Wildcat 4 door. My 75 Electra has a 2.73 posi and my 67 Riviera has a 3.42 posi. If your car was sold new in Canada, you can order the VIN information from GM Canada and you'll see if your car has the G91 option (perf axle with posi). It's also possible to get similar information from the Sloan museum even if your car wasn't sold new here but they don't have the information for all 1970 Buicks (they miss some months of 1970 and all the 1971 model year).
