I wrote this because I see a lot of info posted about lockers. Sometimes it's not right, sometimes it's incomplete, and sometimes it's very biased. I tried to put together a list of commonly available lockers and how they work. I know I missed some stuff and probably got something wrong. It would be GREAT if this could be made a sticky. I know this stuff has all been covered before, but it always gets buried, and it's the second most popular question behind "What gears should I use?"
Additions/Corrections are welcomed. So here goes:
Lockers as I know them:
There are several types of lockers and limited slips out there. In my mind, there are three types of hard lockers, and several limited slips. First, I'll differentiate between lockers and LSDs.
differential is one where ALL of the torque is sent to the wheel with the LEAST amount of traction. This is why one wheel will spin while the other doesn't.
A LIMITED SLIP
differential allows SOME of the torque to be sent to the wheel with the MOST amount of traction. Better than open, but it WILL still slip when the traction requirement goes beyond the capability of the LSD to hold.
locks the axles together, sending equal power to both wheels, ensuring that the wheel with the most traction turns. A true locker allows some limited differentiation between the wheels. A wheel can spin faster than the ring gear, but not slower. (Parts of this definition were contributed by Weldmn)
Now, lets take a look at the different types of limited slips
Trac-Loc - This is a very popular OEM type Limited slip that uses clutch packs behind the side gears to lock the axle together while allowing the wheels to spin at different speeds. Trac-Loc clutch packs look very much like automatic transmission clutch packs, but smaller. Ford uses Trac-Loc as the OEM limited slip if you purchased your vehicle with a limited slip.
Auburn Limited Slip - I don't know a lot about Auburn limted slips, but I believe they use a set of clutches and springs to provide the tension on the side gears.
Posi-Traction - I have no idea of the internals of a Posi unit, since I've never worked on one, but it's a limited slip like the others.
(Contributed by BlueBronco)
PowerLok is another clutch type limited slip by Dana that is pretty good but pricey for what it is.
(Contributed by Lonestar_Bronco)
Detroit Truetrac - a geared LSD with no clutches
Next up, lockers
. Lockers fall into two distinct categories, with each category having it's own sub-categories. First we'll look at Automatic Lockers. There are two types of automatic lockers: Full Carrier Lockers and Lunchbox Lockers (those that are installed in the stock differential carrier).
PowerTrax Lock-Right - This is a very popular locker that is most commonly used in front axle applications. It is intended for light to medium duty wheeling, and will most likely fail when used in the rear of a heavy vehicle with large tires or a lot of horsepower.
PowerTrax No-Slip Traction System - PowerTrax does not call this a full locker, but it is. Basically, it is a modified Lock-Right with something they call a Synchronizing ring that eliminates the harsh engagement commonly found in the Lock-Right. I had one of these in a Full Size Jeep Cherokee, and it worked very well. I installed one in the rear Dana 44 in a Jeep and it broke as the guy pulled out of my parking lot. The syncronizer ring had a flaw and broke in half.
Detroit EZ-Locker - The EZ-Locker is basically the same as the Lock-Right. I have had both lockers, and visually there is very little difference between them. In use, the EZ-Locker seems to be smoother than the Lock-Right.
(Contributed by BlueBronco)
There are 2 other lunch box lockers . . . the Aussie and the QuickLok.
These all basically work the same way. A set of tooothed clutches replaces the spider gears and provides full and positive engagement of both axleshafts.Full Carrier Automatic Lockers:
Detroit. This locker replaces the entire carrier assembly with a much stronger unit. The Detroit is the Gold Standard in lockers, and is suprememly strong. It was originally designed for military use. In fact, there is one exception to the carrier being replaced: 14-Bolt GM axles. The 14-Bolt carrier was designed to take the Detroit internals. That's why you pay so much less for a Detroit for a 14-Bolt. You don't need the carrier. Detroit lockers are ALWAYS there, and have quircky on-road driving charateristics. Off-road, Detroits are awsome.
GM offers the Gov-Loc, which is a GM OEM full carrier locker available in their Corporate axles. This unit normally operates as an LSD, but a counter-weighted locking mechanism locks the side gears together when the wheels have a speed differential of something like 100 - 200 RPM. It makes a very interesting "BANG" when it engages, and if you ever saw one you would be afraid to have it engage. They seem to work well, though, and GM has offered it for decades.Selectable Lockers
allow the axles to operate as open differentials until the vehicle operator engages the locker. There are at least 3 types of selectable lockers available: Air Operated lockers, Cable Operated lockers, and Eletrically operated Lockers.
The biggest player is ARB, and they are the Gold Standard of selectable lockers. ARB lockers require additional air system plumbing and compressors to operate, and they cannot be installed in a driveway by shade-tree mechanics. ARB installation is very complex, and unless you've done it before, it is a job best left to a shop.
The Jeep Rubicon uses a strange air locker from some company from Japan. It uses two little electric solenoid/compressor assemblies mounted to the frame rail. I have not seen these lockers sold independently.Cable-Select Lockers:
The OX Locker is the first commercially marketed cable select locker, and has had mixed reviews. The biggest complaint is with the cables binding up and being unable to engage/disengage the locker.Electric Lockers:
(This whole section contributed by BlueBronco)
Eaton makes the E-Locker and Auburn makes the Elected, and Detroit makes the Electrac. These electric selectables all work differently. The Electrac is like a True Trac limited slip when off and a detroit when on. The Eaton is like an open diff when off and is spooled when on. The Elected is like a ls when off and a locker (I think) when on. The Auburn is very complicated design wise. The Eaton doesn't have any external solenoids on the cover to whack but Detroit has resolved this on there newer designs as well.
Corrected by Weldmn
Toyota has had an electric locker available for it's axles for many years. You can buy this locker from TRD.
And then there are Spools
A spool is a device that physically attaches the axleshafts to each other, permanently. There is no differentiation. There are a lot of different opinions on spools, but I will leave that debate to others.
There are three types of spools: Full spools, mini-spools, and Lincoln Lockers.
Full Spools replace the carrier and are very strong.
Mini-spools are like lunchbox lockers, in that they replace the spider gears, but use the stock carrier.
Lincoln Lockers - so-named because Lincoln is a famous brand of welder. A Lincoln Locker is nothing more than an open differential with the spider gears welded together. This is by far the cheapest method for locking a differential.
I will say this about spools:
You will wear your tires very quickly if you drive a spooled vehicle on the street for any period of time. You will chirp your tires whenever you make a turn, and it will drive very differently than a vehicle with a locker. That said, many people have spooled their rear axles and are happy with the results.
Some will say they have even spooled their front axles. They even sometimes claim that it behaves as if it wasn't there.
I have this to say about that:
DO NOT SPOOL THE FRONT AXLE. You will be unable to steer. Yes, you can take it out of 4WD to steer. You will get tired of this very quickly. You will be MUCH happier with a lunchbox locker in the front. There, I said it. I know this is a controversial subject, but I feel very strongly that front axles should not be spooled.
Again, please feel free to update/correct this list. I'm not trying to promote any one locker over another, but I constantly see people asking about them, and have never seen anyone put a definitive list together.