posi vs limited-slip?
Thread Starter
Melting Slicks
Joined: Feb 2000
Posts: 3,052
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From: Vancouver BC, Canada
posi vs limited-slip?
What (if any) is the difference between Positraction and limited-slip differentials? I familiar with the terms '1-way' and '2-way' limited-slip, and understand they use spring loaded wet clutch packs to lock the half-shafts under certain conditions. I am also familar with Zexel-Torsen style diffs (using Invex torque-sensing planetary gears).
Is Posi just and old term? What type of gear oil should I buy?
Is Posi just and old term? What type of gear oil should I buy?
Safety Car
Joined: Apr 2001
Posts: 4,795
Likes: 1
From: Regina Saskatchewan, Canada.
Re: posi vs limited-slip? (jonjollyf4)
I think all Vettes 68 and later had posi. Some of the oddball 3 speed cars and such had a right legger. Not sure exactly which cars but it's safe to say that 69 and later are all posi. I'd like to have an air locker some day, just like the 4wd guys.
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Brett Foote
Team Owner
Joined: Jul 1999
Posts: 26,545
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From: Huntersville NC
Re: posi vs limited-slip? (flood)
posi traction is GM's name for their limited slip rearend.
Now, can anybody tell me what a "Delcotron" is?? :lol: My 68 service manual doesnt use the word "generator" or "alternator"..... only "Delcotron" !
MJ
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
Re: posi vs limited-slip? (MNJack)
Posi-traction is most definitly a trademarked name. Ford has one and so does Caddy.
Someone a while ago mentioned all Vettes from some year had Posi. 2 ways to check. floor it and both wheel should lock up. Or floor it on a turn.
Another way is jack up both rear wheels. turn one side and the other will turn in the same direction. No posi and the turn in opposites. I think.
If you can steer with your rear wheels and throttle you most likely have it.
Someone a while ago mentioned all Vettes from some year had Posi. 2 ways to check. floor it and both wheel should lock up. Or floor it on a turn.
Another way is jack up both rear wheels. turn one side and the other will turn in the same direction. No posi and the turn in opposites. I think.
If you can steer with your rear wheels and throttle you most likely have it.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: posi vs limited-slip? (inferno-vette)
There is a difference between the two. Limited slip is just that, it alows limited slipage and posi-traction it give full traction = no slipage.
Paul
Paul
A limited-slip in a type of high-traction differential. A posi-traction is the GM name for this limited-slip differential. A limited-slip is never locked, although it may appear that way. Both axles are free to turn at different speeds at any time. All they have to do is overcome the friction of the clutch packs. The preload from the spring or springs provides very little application force. The force comes from pinion gear torque. The more torque going through the pinion gears, the harder they push on the clutch assembly. All you need is an axle input torque differential (caused by uneven friction coefficients or different rotational speeds) to cause the differential to do its thing.
There are only two differential types that lock the axles together. The only one suitable for street use is the Detroit Locker (not available for the 63-79 Corvette 8.375" ring gear case). A spool is race-only piece. In a DL, the only way the axles will unlock is when cornering under light to moderate throttle. The dog clutches will not unlock in a straight line or even in a corner if there is sufficient torque going through the differential.
Really, this information isn't too hard to find through reputable drivetrain sources.
Safety Car
Joined: Jan 2000
Posts: 4,143
Likes: 0
Re: posi vs limited-slip? (Stingy74)
I think all Vettes 68 and later had posi. Some of the oddball 3 speed cars and such had a right legger. Not sure exactly which cars but it's safe to say that 69 and later are all posi. I'd like to have an air locker some day, just like the 4wd guys.
Le Mans Master
Joined: Apr 2002
Posts: 7,281
Likes: 5
From: Boston
Re: posi vs limited-slip? (Bill W)
You must have gotten that perspective off an internet forum from some Supra guy.
Posi looks about the same as limited slip that's right but normally a posi is a stronger unit than limited slip, it "grabs" more.
http://emporium.markwilliams.com/pro...=22&np=22&fp=1
http://www.markwilliams.com/pdfcat/pg14.pdf
No flames, just :cheers:
[Modified by inferno-vette, 12:50 PM 7/31/2002]
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
Re: posi vs limited-slip? (inferno-vette)
Not that it matters but if fords have posi its like calling pespsi a coke.
Fords- traction-lok
Cadillac - mentions controlled differential. It goes on to say that it isn't of the positive lock type. It will release before an excessive amount of torque is directed to one rear wheel. That doesn't make sense to me.
Forgot to mention. Limited slip is the generic term for the differential.
Posi-traction is a limited slip differential
Traction-lok is a limited slip differential Thats what you would see in a shop manual or owners manual.
Ones a coke and the others a pepsi but both are colas Most people say 'coke' when they mean cola. Same with posi.
[Modified by Techno, 6:06 PM 7/31/2002]
Fords- traction-lok
Cadillac - mentions controlled differential. It goes on to say that it isn't of the positive lock type. It will release before an excessive amount of torque is directed to one rear wheel. That doesn't make sense to me.
Forgot to mention. Limited slip is the generic term for the differential.
Posi-traction is a limited slip differential
Traction-lok is a limited slip differential Thats what you would see in a shop manual or owners manual.
Ones a coke and the others a pepsi but both are colas Most people say 'coke' when they mean cola. Same with posi.
[Modified by Techno, 6:06 PM 7/31/2002]
Le Mans Master
Joined: Sep 2000
Posts: 5,635
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From: Orlando Floriduh
Re: posi vs limited-slip? (Techno)
Posi-traction became standard in 1970.. It was an option in 69 but most 69's had posi as it was require for most engines and gear ratios. If you jack both rear wheels off the ground and spin one wheel by hand and the other wheel spins the same direction it is posi- . If the other wheel spins the opposite the it is not posi. Simple test... :D no :boxing boys
Advanced
Joined: Jul 2002
Posts: 68
Likes: 0
From: SLC Ut
Re: posi vs limited-slip? (Turbo-Jet)
What (if any) is the difference between Positraction and limited-slip differentials? I familiar with the terms '1-way' and '2-way' limited-slip, and understand they use spring loaded wet clutch packs to lock the half-shafts under certain conditions. I am also familar with Zexel-Torsen style diffs (using Invex torque-sensing planetary gears).
Is Posi just and old term? What type of gear oil should I buy?
Is Posi just and old term? What type of gear oil should I buy?