ok on rear ends, what is posi and limited slip? what is it called when both tires spin and not just one spinning or one spinning faster then the other? i was just wondering and for some reason i just dont know even though im around cars all the time , thanks

Hey 77,

When both wheels spin, that's a Posi (Positraction) rear. One wheel spinning is referred to as an "Open" rear.

Posi rears come in two basic categories:

1) Limited Slip which lets one wheel break loose when going around a corner. The unit will lock up again when you apply the brakes.

2) Locked Posi unit, mostly used in racing applications as it does not break free and can be difficult in rainy weather.

Dan

Hey 77,

When both wheels spin, that's a Posi (Positraction) rear. One wheel spinning is referred to as an "Open" rear.

Posi rears come in two basic categories:

1) Limited Slip which lets one wheel break loose when going around a corner. The unit will lock up again when you apply the brakes.

2) Locked Posi unit, mostly used in racing applications as it does not break free and can be difficult in rainy weather.

Dan
Actually it is my understanding that "Positive Traction and Limited Slip" are exactly the same thing. A locker is locked at all times and it is not a Posi in the true sense. A Locker is a hard connection between the two axels. It will cause a serious wear on the tires and in Rain it will create an problem called over steer, well even on dry pavement in acceleration around a corner you'll get lots of over steer. You are correct in saying that the locker will not detach the outside axel during cornering it can't.

PowerTrax and others make a piece that will try to act like a Posi unit when in corners and a locker when driving straight. They are way better than the Posi which has clutches like your Automatic Transmissions and uses fluid very close to that used in a automatic tranny and can need repairs or replacement of the clutch packs. A locker will never need that. The Power Trax will also cause over steer in hard acceleration around a corner. It will try to disengage and you'll get a ratcheting effect on the rear wheels. Over time I am told that will subside a small amount.

As you know over steer is where the drive wheels try to drive the vehicle in a straight line over powering the steering.

Anyway that is what I was always taught about the differences. Limited slip and or Positive traction devises require one wheel to slip (thus limited slip denotation) before the other will pick up the slack and in some cases yes the brake is helpful but only if your stuck in mud or something like that.

Here is a good reference source (Explanation)

http://www.drivetraindirect.com/html2/things10a.htm

Posi and limited slip refer to the same thing. Locker differentials are normally used only for drag racing applications where no cornering is involved.

This site has a good explanation of differentials in general, with lots of illustrations and animation.

Howstuffworks - How Differentials Work (http://www.howstuffworks.com/differential.htm)

thanks guys for clearing that up, just something iv never ran across

Spool is the same thing as a locker. Don't run a spool/locker if you are going to be driving this on the street more than strip

Posi/Limitedslip=Street/Strip
Full Spool/Locker=Offroad/dragstrip

-Eric

Here's one more take:

A posi or limited-slip differential uses the friction between clutches or cones to couple both axles when going straight and disengages the clutches/cones to decouple the axles when going around corners.

A locker is a gear-like apparatus that solidly locks both axles when going straight, but it's spring loaded and de-couples when going around corners. I've had these before and they work fine, but can be a bit noisy when they de-couple.

A spool solidly connects the axles together and they cannot de-couple (unless you break it!) - this is for drag strip duty and doesn't work well on the street no matter what the weather.