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Old 01-03-2007, 10:32 PM
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posi = limited slip, right??

the other day I caught the tail end of a conversation that went like this ".... naw you don't want to go with a limited slip differential, go with a posi you'll be much happier." I didn't want to interrupt and impress everyone with my stupidity, but I always believed posi was the same as limited slip. have I totally missed something here? there are just three types of differentials, open, limited slip, and spools, right?

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Old 01-03-2007, 11:04 PM
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There just different methods from what I understand. Some have clutches some dont' etc. I wouldn't mind knowing for sure either. Can anyone shed some more light?
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Old 01-03-2007, 11:26 PM
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From what I understand Positraction was the name Chevrolet called their limited slip differentials. Ford called it Trac-Lok, MOPAR called it Sure Grip and so on...
I've heard people call open differentials "limited slips", they would say "well it limits wheel slip because only one wheel turns" When I hear that I laugh to myself and usually don't say anything.

EDIT:
I found this...http://en.wikipedia.org/wiki/Limited_slip_differential

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Old 01-04-2007, 12:05 AM
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True, positraction is a brand moniker, but for lack of a better word, i'll use it

Open diff- has side gears. wheelsare independant of each other, either can spin.


limited slip- has a clutchpac or gear pac that links the axles together but still allows the wheels to turn some in relation to each other hence limited slip. Allows turning without scrubbing the tires

Positraction, also called a locker- axles are locked together by a gear or dog system that allows no slippage between the wheels. Can be engaged or disengaged on demnd.

Spool- As it implies. The axles are joined in the center buy a splined tube that is fixed to the ring gear. For straight line used or where scub is not a problem only. pita on the street.
Clear as mud?
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Old 01-05-2007, 01:56 PM
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Quote:
Originally Posted by 61bone
True, positraction is a brand moniker, but for lack of a better word, i'll use it

Open diff- has side gears. wheelsare independant of each other, either can spin.


limited slip- has a clutchpac or gear pac that links the axles together but still allows the wheels to turn some in relation to each other hence limited slip. Allows turning without scrubbing the tires

Positraction, also called a locker- axles are locked together by a gear or dog system that allows no slippage between the wheels. Can be engaged or disengaged on demnd.

Spool- As it implies. The axles are joined in the center buy a splined tube that is fixed to the ring gear. For straight line used or where scub is not a problem only. pita on the street.
Clear as mud?

In the generally accepted vernacular of the last 4 decades,

a posi is any limited slip, allowing some slippage between axles even under straight line power or power while turning, hence the name.

a locker is a locker, no slippage allowed under power, the outside axle disengages for differential action only under coast conditions. Solid or open, no in between.

and spools are spools, ZERO slippage allowed. Locked solid all the time.

There are various designs for each type of "carrier assembly".

Spools are dangerous for street conditions due to massive understeer. Lockers can be dangerous for the same reason, unless you know how to drive them. Excessively tight posis in slippery conditions can be hazardous also. Many people argue this point until they end up in some ditch.
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Old 01-05-2007, 04:17 PM
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Quote:
Originally Posted by 61bone
Positraction, also called a locker- axles are locked together by a gear or dog system that allows no slippage between the wheels. Can be engaged or disengaged on demnd.

Spool- As it implies. The axles are joined in the center buy a splined tube that is fixed to the ring gear. For straight line used or where scub is not a problem only. pita on the street.
Clear as mud?
Just a little clarification.

The majority of lockers cannot be 'engaged or disengaged on demand'. Examples are Tru-trac, Detroit, Auburn. Selectable lockers are exactly that, you can switch them on or off, from open diff to fully locked. Examples are the ARB locker & OX locker.

Loosely used, a 'spool' refers to any means used to completely lock the two axles rotations together permanently, such as a store bought spool or by welding the spider gears together.

As for the original question, in my experience a 'posi' and a 'limited slip' are the same thing, and are 'branded' by the specific manufacturers as listed by Blazin72.

Mud is mud, any way you throw it.
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Old 01-07-2007, 11:48 PM
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And, just to confuse things even more, GM has been using the Positraction name on Gov-Lock differentials lately.
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