New gears...

Hey guys. I am about to re gear my 75' cj5. My question is what is the difference in a spool and a locker? What would be the wiser option to run. I have dana 44 rear and 30 front. I am going with a 4.56 gear ratio. I use my jeep for offroad mostly, but I do drive it to the trail on occasion.

 

A spool positively locks both axleshafts together. NO give between them. This can wear tires, cause handling quirks on slippery roads or trails, etc. They are also harder on axleshafts because there is no give.
A locker is a unit that WHEN UNDER POWER, either forward or reverse, the axleshafts lock together. However, under coast conditions they will unlock to allow the axle shafts to rotate at different speeds. These also can have handling quirks on slippery surfaces under power. On hard pack though they do release and are not as hard on axle shafts. Most lockers are noisy and can bind and release causing a kind of jumping sensation, especially at low speed in a sharp turn. This applies to the automatic lockers like Aussie, Detroit, Lock-Rite, etc.

There is another type of locker that is controlled by the operator. ARB air lockers, Electrac, etc. Most act as a normal open diff when unlocked, then like a spool when locked. There is one, I think the Electrac but am having a brain fart right now, that when unlocked is a limited slip then when locked is a spool.

A limited slip, or commonly called a Posi unit or Positraction Unit (GM's brand name for limited slip) is a unit that will bias torque toward the wheel with the least traction, but that tire can still slip if no traction at all. It's a helper, but not super positive. Very street and mild trail friendly however.

 

A spool locks the axle shafts together. They will not turn independantly from each other. Unless something is broken. You get 100% traction 100% of the time to each wheel. If you live in snow country, it's not recomended to run a spool because the rear end will spin out from under you very quickly. When you turn the jeep, the outter wheel will drag around the corner becuase the inner wheel will turn slower than the outter. Or the inner will drag because the outter is trying to go faster. Causes faster tire wheel and squeeling tires each time you turn sharp.

Lockers, detriot, etc, have a way, using springs or clutches or cones, that allows one wheel to spin faster than another but never slower. So if you go around a corner, the inside wheel is driven, the outside wheel can "unlock" and spin faster than the inner. But if you are stuck, each tire will give 100% traction because no tire will turn slower than the other.

Personally, I like both spools and lockers. My jeep I'm building right now will have a spool in the rear and it will be my DD. I've ran lockers in the rear and sometimes they unlock with a bang and a lurch.

There is also something called a selectable locker. You choose if it's locked or open. Locked and it's like a spool. Off and it's like a regular diff. Probially the best but more money. Ox locker, air locker are two types.

Personally, I'd have an Ox locker front and rear if I had the cash. If money is an issue, run an Aussie locker in the front and rear. Or Aussie front and spool rear.

DO NOT RUN A SPOOL IN THE FRONT. you can't hardly turn it.