do all C4's have real posi where the tires spin the same way?

or does one of urs spin backwards?


its a 91 6 speed , so dana 44 3.45 ratio.. what my rpo says

 

I don't believe any didn't have it? Would be weird for a performance vehicle... If it is spinning backward like an open diff I would think the clutch packs (pretty sure that's what the c4 uses) are shot... I'm not great with posi though as most of my vehicles have had abs posi or Eaton lockers...

 

If you will jack up the back of your C4, with the trans in "Park", you'll find that you can't rotate the rear wheels by hand

If you put the trans in "Neutral", then rotate one wheel, the other wheel will rotate in the same direction, and the driveshaft will rotate. This is because of the "posi" clutches in the diff. All C4's have Posi differentials.

If you try this on your RWD Malibu, you'll probably find that you will be able to rotate one wheel, and the wheel on the other side of the car will rotate backwards. This is because your Malibu does NOT have "posi" clutches in its diff.

 

might not be as weird as you think, a lot of performance vehicles are limited slip rear ends

 

I meant it would be for a performance vehicle not to have one. At least a sports car type.

 

All C4s came with a limited-slip diff. If your wheels are turning in opposite directions with the trans in gear, then either something is really broken in the diff or someone raided it for parts (i.e. robbed the clutch disks out of it). Even a worn out posi should have some resistance to differential movement.

 

both of mine spin the same way. it's a 6 speed manual so it was in neutral. but i do know most of the camaros and z 28's i have owned usually have 1 tire spinning backwards which is limited slip correct? or am i mistaken. i thought limited slip which still will burn both tires off has one spinning backwards. thought only a true posi rear end had em both going the same way.
i have had acouple z28's that were i think 373 gear . that one spun the same direction, that was in a 78 z i think it was. with 4 speed. i know all the gen 3 camaros i have ever had were one tire spinning backwards. they all would leave 2 black marks when spinning the tires though

 

Positraction is just a brand name of one type of limited slip differential, just like Ford's Traction Loc. Both are clutch-type limited slip diffs, but there are other types too. All are limited slip, and they have the same function: to provide resistance to the tires spinning at different speeds/directions. So no, if one spins forward and the other spins backward that diff has no type of limited slip. Many, many F-bodies were built without limited slip diffs. No C4s were. It sounds like your C4 has a proper-functioning positraction diff.

 

Brian, it's obvious you don't understand how a differential works. Hopefully, this video will explain it to you.


There is NO WAY the two rear wheels of a car will spin in opposite directions when the driveshaft is applying power. The observation you have of opposite rotating wheels is when the rear wheels are elevated, and the driveshaft is stationary. At this time, the "spider gears" are rotating on their shafts, and torque is being transferred from the driven axle to the opposite axle by the rotation of the "spider gears". The "ring gear" and the "pinion gear" are stationary at that time.

 

ya, i am getting mixed up with spools, i think but still not sure how some of my old cars that had one tire that spun backwards, still burn both tires off. doesn't matter really i guess. i know my current car both spin the same way and i smiled when i saw it. and yes hotrod roy. car jacked up with all 4 tires off the ground, engine off in neutral..

like my z 71 truck. rear end jacked up engine off. spin one tire forward...other tire spins backwards... but i promise you that thing will go sideways quite easy with both tires spinning every time it snows if its not in 4 wheel drive. so ya. i guess i always kind of considered that limited slip.. but it is actually just a standard rear end . then limited slip both tires spin same way but allow you to be able to make a right turn at a red light without one tire squealing at 4 miles n hour not even trying to make them spin. then the spool.. which must of been what my 76 trans am had in it where both tires are just locked, cause that thing would do exactly that at a right turn, every time. 1 tire just barely sqeualing taking off around a corner.. or it was spiders wleded...

 

Not every type of limited slip diff works like the posi in your Corvette, so that might explain your truck's behavior. But just rest assured that your C4 has limited slip and seems to be working correctly.

 

If I were to guess, that Z71 has the G80 which iwhictype of locking differential... it locks clutches and spiders once it senses slip but otherwise acts like an open diff.

 

If it was locking, wouldn't that lock the wheels together if the rear end was jacked up, thus both wheels would spin the same way? Assuming it's an auto locking diff VS manual?

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i don't know, like roy said.... i know on dry pavement that truck is 1 tire fire but it will cook that 1 tire right off, still have the black mark 100 foot long in my driveway to prove it after 2 yrs.. that sucker smoked the tire in first and second gear until i let off the pedal.. all the way down the driveway.onot a little 26 inch tire either, they were beefy hancook all terrain tires. i was getting ready to buy my bf goodrich all terrains so i didnt care. melted half tread of tire off in one burnout .. had a hemi dodge guy in the driveway talking smack about my chevy lol... told him lets see if that thing can do this.. his jaw hit the floor. but in snow n stuff both tires spin sideways course the truck has like 250 k on it and the vortec runs strong but the rear end is worn im sure. should just retire that old truck and put the heads on the vette but it still has a lot of snowy icy roads to get me to work on. i know this is a corvette forum but damn i love them old silverado trucks from the 90's..... they really are like a rock 98 z 71.. runs like a champ with 250 k.

 

The G80 will spin like an open diff on stands. It only locks if there is enough of a difference in speed between both sides and, if memory serves me correctly, will unlock at higher speeds regardless of if one tire is now slipping.

 

Your Z71 has a different type of rear. It actually has a locker as described above. One wheel will start to spin before the rear will lock the other axle. If you are spinning one wheel then hear or feel a clunk from the rear it just locked up the other axle so they spin together for better traction.

Gary

 

If both spin in snow but only one on the dry, I'd wager you just have an open diff. Coefficient of friction is low enough that both should spin.

 

Wait I can’t keep up. Do we like Shmee again?