What exactly is the difference between Posi and Limited slip?

 

nothing, they are the same

 

yup


why are the 2 confused?

i dont get it

 

"Positraction" is a Chevrolet name for a limited slip differential. Over the years every manufacturer has offered a limited slip, and each one gave it a unique name in their literature. Ford used "Traction Lock", AMC used "Twin Grip", and Pontiac used "Anti-Spin". The Chevrolet name just seems to have stuck in popular culture, so now it is popular to just refer to any limited slip as a "posi". Sort of how everyone calls a copy machine a "Xerox" machine, whther it's actually built by Xerox or not.

 

Pontiac used "Saf-T-Trak"

 

It may have been Buick or Olds that used "Anti-Spin" then. Someone used "Dual Grip" too...

 

dodge currently uses anti spin

 

biggest differance is the spelling

 

Is that what they call it now? I remember they used to call thier limited slip rears "Sure-Grip".....

 

That's what's on the build sheet for my neighbor's 2004 Ram

 

So then how come when some people do a burn out only one tire will spin, when other people do it both tires spin? Whats that called?

 

I've heard that there are different types. One is better for drag racing because it quickly balances out the power to the wheels. The other is better forroad racing because it is more gradual and is less likely to upset the car's balance in a turn.

There are some that can be rebuilt and some that can't (I guess).

Then there's the "locker" which I think is actively engaged as oppsed to passively reacting to traction conditions.

What is what I don't know, and I think it would be good to find out.

 

I'm used to seeing lockers in drag racing and different posi types for road racing, i don't know about which type of posi is better for either.

A Eaton type Limited slip diff uses plate clutches, and can be rebuilt. An Auburn type (cone clutches) cannot be rebuilt. A Zexel-Torsen type uses worm gears instead of clutches, so it shouldn't wear out or need to be rebuilt.

 

The ones with one wheel is either a bad limited slip or open rear, both tires would be a limited slip rear

 

If only one tires spins throughout the burnout then it's a bad limited slip or a peg leg.

If one tire starts to spin, and then the other one catches up it can still be a limited slip, and there's not necessarily anything worng with it. There a several types of LSDs. Some need to sense a difference in wheelspeed before engaging, while others just respond to torque.

 

Auburn posi can be rebuilt!!!!!!!!

 

The cone type? THEY told me they cant. They do make a disk type, and yeah. it can be rebuilt.

 

Positraction=Limited slip. Just a trade name. Terms are interchangeable.

Lockers are an entirely different animal. They will act as an open diff unitil wheel spin prompts them to lock, then, it is basically a spool. Both wheels are locked together with NO slip.

Lockers are fine, and work rather well, however, the drawback is (at least for the detroit lockers I have used) they are NOISEY! After the installation, took the car for a test drive, and I thought I had done something wrong, when the rearend locked, it sounded like it was getting ready to grenade. (found out later that is NORMAL??????)

 

Ok whats the deal with front wheel drive cars are they limited slip or what I don't know how they even work

 

They can be limited slip, they use a diff just like RWD cars.

 

if you want both wheels to spin when u do your burnouts, u can always weld the axle..

 

And that's all well and good till you wanna turn...

 

o yea, expect to chirp the tires when u turn

 

Well i've got a 91 RS.......engine and tranny are new but the diff is still the same. I have about 123,000 miles or so on the car it self. When I do a burn out I only leave one line. When I do a circle the inside one is a dark line and the outside one is very light, can hardly see, sometimes you can't. Would this mean my diff is bad???? It doesn't make an weird noises and doesn't clunk or anything.

 

no, your differential is fine. Your car never came with positraction from the factory. You have to install one yourself like I did. BTW, eaton is the best.

 

So then is what I have called an open rear end???? Eaton huh, I'll remember that.

 

yes, you have a non posi, open rear.

 

wow. All this time I thought I had a limited slip cause only one tire spun. Then to find out that posi and limited slip are the same thing, I feel like a dork thinking they were two seperate things. But here is another question, why would you want posi over open rear???? Or open rear over posi?????

 

2 tires instead of 1 gives you twice the rubber and twice the traction.

 

A posi allows you to send power to both wheels, instead of only one. This allows for better acceleration through increased traction.

I'm not sure why you'd ever want an open rear over a posi...

 

Well I wasn't sure if you would want an open rear, so I asked somebody who would know better than me, You guys. So why did GM make them with open rears???

 

cheaper, and about 50 times more durable than a posi. no clutches to wear out.

 

open rear is easier to drive on the wet ground, especially when turning. My rear kicks out pretty easy when I turn and it's wet outside.

 

On the subject of which type is better for what application, I'd definitely recommend a clutch type posi over a locker unit for road racing and regular street use. The only thing better than a locker for drag racing would be a full spool setup. Lockers work awesome for straight ahead total two wheel traction, but like the other guy said, they're noisy and can also be jerky around corners. I run a powertrax locker unit in my 69 Camaro twelve bolt rear, and it's noisy and catches the gear teeth funny around corners sometimes whicn causes a loud clank and causes the car to jerk or lurch for a second. I have to agree with the other guy on this note too, the first time it did that, I thought I'd broken something! I have a clutch type posi in my 89, and it's much smoother and quieter than the locker unit, making it much more suitable for windy roads and regular street driving.

 

Don't mean to hijack this post or anything, but my 88 base camaro has a 2.73 open diff that I'm soon going to make posi. I'm looking at the auburn posi on jeg's for 2.73's so I can use my gears that I already have. Do I want the 26-spline posi or the 28 spline posi? Is the posi unit all I need? How hard is it to put in the posi? I'm in autos at my school so I have all the tools, a lift, etc... Thanks.

 

Hey Morgan, if your 88 still has the original rearend, it should have 26 spline axles in it. The one other thing you'll probably want to order with the posi unit is the basic gear installation kit that comes with the pinion bearing, crush sleeve, marking compound, and shim assortment. This should give you what you need to complete the installation as long as your auto shop has a dial indicator with a magnetic base and an inch pound torque wrench. If you've never done one before, you should definitely have your instructor or someone with some experience help you set the new carrier up in the housing as it's crucial to get the contact pattern correct on the gear teeth.

 

You could also step up to 28 spline axels when you change the posi. They are about 10-15% stronger than the 26s. You will also have a wider assortment of posis to choose from with 28s.

A locker is a bit unruly on the street. I'm running one in my Camaro and my Blazer. It takes some getting used to, but I love the traction and the durability. If I drove the car daily I would have used a clutch type posi though.

 

He won't need the pinion bearing and crush sleeve, as he wants to keep the same gearing, so he won't have to remove the pinion gear.

 

As long as the pattern checks out that's right.

 

usually the pattern is fixed by shimming, i've never done one that required doing anything to the pinion gear.

 

Usually is the key word. Assuming that you can set the backlash with the carrier shims, and the pattern is exactly like it was before then you won't need to touch the pinion. This should be the case, but that absolute word "always" is what will get you into trouble if you don't check things out.

On a side note, since you're using used gears make sure to check the pattern before swapping the new differential in. Then, make sure that the pattern achieved with the new differential in place is exactly like the old one. Pay most of your attention to the coast side of the gears.

 

Yeah I ran a PowerTraxx locker in my 83Z 5 speed,and daaaaaamn it was great as far as both tires spinning..but if I went slow like in a parking lot and turned it would "CLANK" and jerk and people would look at my car like "wow what a $hit box"
so I learned to push the clutch in at slow turns and that helped..but sometimes leaving a stop sign and turning left or right the locker wouldnt be fully engaged and when I started cranking on it after it got going in a straight ling it would let out the loudest clank and people would always stare
anyway I finally took it out and it looked mint so I sold it!
I'll stick with the clutch set-up now unless I was going to be fully draging then the Powertraxx would be a great choice or a full spool

 

Hmm, wonder if yall had older models of PowerTrax lockers, mine is very quiet, never hear it other than in a parking lot doing full lock turns at like 1 mph and then it's just barely, I don't think people outside of the car can hear it much at all (certainly not very well over the exhaust...) Over 5mph turns I've never heard it clicking.

Every once in a blue moon it will get it wound up or whatever and get a clank/lurk, but that is a rarity and it's a daily driver. I have zero complaints about it... Mine had street and track springs, ran the streets obviously. In the long run the posi I put in my 86 IROC is starting to wear out, get one wheel peels occasionally, while the powertrax is still going strong in my 87Z...

 

ok I have a question. Whats Spool??? I got a moser rear-end & axles in mine w/posi. There was another 1 with ¿spool?

 

it replaces the posi and locks both axles together. Crappy to drive on the street.

 

Hey Ray, mine is an older unit. I think I bought it around '95 or '96. I'm also wondering if yours is the performance locker or the no-slip locker. I've noticed they offer those two different units for some applications with the "performance" locker being a little more spendy than the "no-slip" unit. I do have a little confession to make though. Mine came with two sets of springs too and I used the strip springs. Maybe I oughta take it apart when the weather gets a little nicer and try the street springs instead! I used the stiffer springs under the theory that quicker engagement of the gear teeth might cause them to wear less and reduce slippage of them. Guess that'll teach me to come up with my own theories eh?

 

Then what is a detroit locker? Is that sometimes posi, sometimes not?

 

A locker is nothing like a posi. It doesn't use clutches at all. A locker is more like and off and on spool. In a straight line the locker acts just like a spool with full traction to both tires. Around a turn the locker will unlock and allow different wheelspeed for the two wheels. A locker will make some noise as it locks and unlocks, and sometimes it can jerk the car a little, but the beneift it that they are nearly indestructable and never wear out. A posi may be seamless in operation, but they can and do wear out, and there is a limit to how much power they can handle. I've seen and heard of posi units breaking and burning up all the time. I've only ever read about a locker breaking once, and that was on a 700+ horsepower truck with an additioonal 200 horses of giggle juice. The truck was a 4X4 mud bog racer, and the challange was 4 Wheeler's annual competition of the baddest trucks in the land. This was the only truck that actually made it through the mud pit under its own power, even though it broke the front locker during the run. That truck als0 had a Rockwell 2.5 ton rear axel and a Dana 60 front, so it was packing some serious hardware. If that's what it takes to break a locker I think we're all safe!

 

were can you get a locker and how much do they go for. i have been considering this for a while.

 

I bought my locker for my 83 Z from JEGS...but like said above
if you want your nice looking car to go smooth then save your money and buy a clutch type!!!!! It will be well worth it,Id never go back to a locker unless it was for a car set-up only for drags.