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Discussion Starter · #1 ·
what is a spool?? and what is a posi?? I hear these words being thrown around but i dont know what they are or what they do?

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92 Jeep YJ with 1 inch shackle lift and a 2 inch body lift running 31's

[This message has been edited by Brent (edited November 15, 2001).]
 

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There are 4 types of differencials. open, limated slip, locker, and spool.

An open dif is just a standerd dif, so if you loos traction under one wheel it will just spin and the other one won't.

a Limated Slip dif usually has some sort of clutch in it to help keep both wheels spinning, so that if you loose traction under one tire, the other one will still put some power to the road.

A locker is one stp further than a Limated slip. It actually locke the left and right axle together so they must both turn at teh same speed. Theye are 2 types of lockers, mechanical (detroit for egsample) and selectable(ARB air locker for egsample). Mechanical ones are allways enguages, but will disengage when cornering to allow for the inside and outside wheel to turn ans slightly different speeds. selectable lockers give you a button in the cab that lets you turn them on and off(much more expensive). Tires tend to wear a little quicker with mechanical lockers than they do with open or limated slip diffs, but not a quickly as they wear with spools.

A spool is even one step further. It permanantly locke the left and right axle together, and your wheels can no longer turn at different speend. This makes tight corners interesting, and also wears tires out faster than with any other diffs. Some people say you can just take an open dif and weld the the (spider?) gears and get the same result as adding a spool for a lont less money, but I would not recomend this, I have heard of welds breaking.

Hope this helps.

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1974 Dodge W100 Power Wagon
Looks beaten up but it's fun.
Slowly becoming less original, 31" tires, 360 2bbl V8, TF727 3 speed auto, NP205 T-case Dana 44 front, Chrysler 8 3/4" rear with detroit locker
 

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Further to what Jarett said, the term "Posi" refers to a type of limited slip. It is not a locker.

...lars

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And further on (un)limited slips, is that they wear out after a while, and begin to act just like open diffs. I've heard people say that the trashlcok (chrysler trac-lock which is a limited slip) is good for something like 20,000 miles.
 

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Excellent summary, Jarett.

Additional info:

Limited slips, lockers, and spools are collectively known as traction-adding devices (TADs). They have an advantage over a conventional "open" differential by having the ability to provide power to more than just one tire. So, when you are out on the trail and you are stuck because your right rear and left front tires are drooping into holes and cannot maintain traction, a TAD would have allowed you to continue on by providing power to one of your other tires that were still maintaining contact with the ground (and this is also why lots of suspension droop is a good thing).

The thing that wears in a limited-slip diff (LSD) are the clutch packs, which can be replaced. When the clutch packs are worn out, it's just like having an open diff. One type of LSD is the Detroit Truetrac, which uses a gear-type design and does not have clutch packs to wear out. The down-side to a LSD is that if one tire is in the air, THAT tire will be the one spinning, not the one on the ground. But, if you apply the brakes slightly, you can trick the LSD into thinking that there is some resistance at the tire in the air, which will allow the LSD to apply power to the tire on the ground.

The ARB air locker and the Toyota electric locker are not really "lockers"; they are switchable spools because they do not allow for differentiation when locked (ie. they will not automatically disengage in a corner). These "command lockers" are great because you can switch them off when on the street, on a sandy side-hill, or when making tight turns on the rocks.


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Greg Sue
85 Toyota X-cab
http://media-north.com/4wd/
 

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Discussion Starter · #6 ·
thanks guys i think u just summed it all up for me

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92 Jeep YJ with 1 inch shackle lift and a 2 inch body lift running 31's
 
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