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1,614 Posts
Discussion Starter · #1 ·
Newb to lockers here and I need some advice / info.

what are the key differences in lockers?
what is the good / bad of the different styles?
what should you look for in a locker up front if its a daily driver and sees more pavement than dirt.

any and all info on lockers would be appreciated

stole this from

Beginner's Guide to Differentials, Limited Slips, Lockers and Spools

When going around a corner, the outside wheel always travels
farther than the inside wheel (circles of different
diameters have different circumferences). Since both wheels
are attached to the same vehicle, it is obvious that for
this to happen, the outside wheel must therefore also travel
FASTER than the inside wheel.

The standard open differential and the limited slip (what
most auto makers offer as a traction-adding device) allow
the outside wheel to be driven (by the engine) faster
through a turn than the inside wheel. This makes for a
smooth driving vehicle with no binding of the drivetrain or
scrubbing of the tires. There is no hopping or chirping of
tires which was common with early automobiles that did not
have a differential. BTW, that's why it's called a
differential, it allows for different speeds between the two

The problem with these differentials is that they operate by
balancing the torque load on both wheels. That is fine when
both wheels have the same traction (and therefore the torque
loads have the same resistance at each wheel). But when one
wheel has less traction than the other (ie: it's on ice,
snow, mud, sand, or even in the air) then very little torque
load can be applied to it because there is very little
resistance. And because the differential wants to balance
the load, BOTH tires end up with very little applied torque.
That's why you end up seeing the wheel with the least
traction spinning: it's spinning because it requires very
little torque. On the other hand, the wheel with the good
traction can't even turn because the torque is too low.

Limited slip differentials try to get around this problem by
biasing the torque so that it gives a greater percentage of
available torque to the non-spinning wheel. In other words,
it doesn't balance the torque, it biases it to the wheel
with the greater resistance or traction. This isn't a huge
amount, typically around 15% I believe. In many cases, this
is all you need (ie: snow covered streets, wet pavement and
dirt roads). But when you're on the rocks or you're going
uphill on a rutted road, a percentage of a small amount of
torque just isn't going to cut it. That's when you need a
locker or spool.

A spool is the exact opposite of a differential. It allows
absolutely no speed difference between left and right
wheels. They are permanently locked together. No matter what
the traction conditions, the engine will always drive both
wheels. This provides an enormous advantage on difficult
terrain. The downside is that it is horrible on the street
because there will be driveline stress and increased tire
wear whenever you drive around corners. On the dirt, it's
not too bad since the wheels can slip but on the street the
traction is too great. The tires will chirp and possibly
hop. Some people use spools on the street but they're a
distinct minority and I'd discourage it. A "welded diff" or
"Lincoln locker" is the same as a spool...but cheaper and
less reliable. Cheaper because no parts are required; you
just weld the differential's gears so that they are frozen
in place, thereby preventing any ability to allow
differentiation. Less reliable because: a) welding weakens
the gears and b) the stresses introduced by this spool
effect often exceed the design specs of the differential's

ARB, OxLocker and some other manufacturers make a
combination differential/spool that lets you choose the mode
in which it should operate. These are often referred to as
manual- or selectable-lockers. For the street, you can turn
the spool off so it will operate like a regular open
differential. Switching is accomplished by a button, cable,
or lever inside the vehicle. For the trail, you can turn
the spool on for maximum performance. No downsides except
for the price and difficulty of installation.

The locker (often confused with a limited slip) is a kind of
automatic selectable spool. Oftened referred to as a
automatic locker, its default state is to lock (hence the
name) left and right wheels together like a spool. In this
mode it operates just like a spool. But when going around
corners, it allows the outside wheel to disengage from the
inside wheel and turn faster by allowing it to be driven by
the ground (as opposed to being driven by the engine). It
accomplishes this by a ratcheting mechanism. Once the
vehicle exits the turn and drives in a straight line, both
wheels lock together again. It is this locking/unlocking
action that is the locker's source of advantage and
disadvantage. It's advantage is that it doesn't result in
the driveline stress or tire wear common to spools. It's
disadvantage is that the point of locking/unlocking results
in sudden over- and under-steer which is particularly
pronounced on sweeping turns (as opposed to sharp turns).
It's enough of an annoyance and disturbance that some people
would prefer the more predictable manners of a limited slip
or a spool. But there are lots of other fourwheelers who
have learned to live with the locker's quirks.

On ice and snow, the spool and locker are probably the worst
choices for highway driving because if there is any wheel
spin, it is always both wheels spinning at the same time.
That means that neither of that axle's wheels can help
control the vehicle's direction. With a limited slip or
open diff, generally only one wheel will spin, allowing the
other to help track the vehicle in a straight line. A manual
locker would also be a good choice for snow/ice-covered
roads because you can choose how it should operate. Having
said that, there are many people who drive their automatic
locker-equipped vehicles on icy roads on a regular basis. It
all depends on your comfort level.

1,614 Posts
Discussion Starter · #2 ·
If you had a Detroit or other auto locker up front would it engage and disengage while still in 2WD or only when there is torque being applied by a powered drive shaft?

Would limited slip up front hinder your turning radius or cause extra wear on the tires?

224 Posts
thanks for finding and sharing

2,835 Posts
I have ARB lockers and love them. I personally would not put any other kind of locker in my Jeep. The freedom to lock and unlock at will is the best. I don't have to worry about it locking up going around a corner or when it is going to lock. Just flip a switch and go. If my lockers are not locked, they become open differentials and drive as if they aren't even there.
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