My buddy drive a mustang with a posi rear end. I want to replace my gears, and I was wondering what was better?? Posi or Limited slip?? And what are the main differences?? Advantages, and Disadvantages??

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Godti
'89 Trans Am (Red)
305 TBI 5spd

 

They are the same thing. GM just calls their posi a limited slip.

 

ok correct me if i am wrong here. Trying to remember the explanation from back in high school shop class.

A true posi allows no slipping of the left or right wheel. I assume most dragsters use this because all they do is go in a straight line.

A limited slip allows well limited slip of the left and right wheel. Here is an example to help me make sense of what i am writing. Lets say you have the steering wheel cranked all the way right driving the car in circles at idle speed, the inside wheel or right wheel is going to be rotating less while the out side wheel is going to be rotating a whole lot more because it has a lot more road to cover. The limited slip allows that right wheel to slip. But when you apply throttle to it it stops the slip and puts equal force to each wheel. hence doing "donuts or shi**y's" as they are called.

Now it you were to take a true posi and drive in circles the inside wheel would be moving exactly the same rate as the outside wheel at any speed, part throttle or full throttle.

And a slip differential will allow a wheel to slip all the time no matter what.

I think that is right, but i may be wrong, feel free to correct me on this.

But yes it street driven cars the posi is often another word used for limited slip. So i would assume they are the same.

 

posi is 50/50 power slip. limited slip doesn't have to be 50/50 but usualy is.

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-Tas
'89 Formula WS6

305, TBI, auto, 14x3 chrome flat based open element with K&N, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

Super GRK_Taz World
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AOL IM: superGRtaz
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Didn't I JUST see a copy of this question somewhere else??????

Lock is right, "Posi" is short for "Posi-traction", which is GM's trademark name for their Limited Slip Differential. Mopar calls (or use to call) theirs "Sure Grip" for the Dana made Limited Slip Differentials. I can't remember what Ford calls their LSDs.

A LSD "limits" the amount of slip between the two rear wheels. If you don't have a LSD, you have the "one wheel peg leg", or as I call it "Unlimited Slip".

What some people are confusing is the fact that a LSD (as on street cars so equiped) does slip a little (to facilitate corners) whereas a "locker" prohibits any slippage between the wheels. This is not a "Posi"... this is a "Locker", which is intended only for the strip.

Yes, this question MUST be added to the FAQ.