Here is my 2c:
The ARB and the OX – debatably the 2 most reliable manual lockers, when engaged, will act as if you are operating with a spool-type diff. This will effectively ‘weld’ your axels together and each wheel will rotate at exactly the same speed when accelerating, decelerating, and turning. That feature is great and predictable off-road but is highly stressful on the axels while on the street and not going perfectly straight (ie. drag racing). But don’t forget that they don’t do anything until you make them – man in the loop to operate - and they are more complex; increasing vulnerability to malfunction or failure. I guess it could be kind-of cool chirping the tire turning into your parking space when you go to the mall, too. The ones below are automatic.
The Tru Trac essentially uses friction via mechanical advantage from several worm gears in the unit to lock the axels under load. There are no ‘clutches’ in this one. I frankly don’t know quite as much about the Tru Trac, but presumably it doesn’t lock on the decel due to the cut on the worm gears and the mechanical configuration. Someone please back me up on this. The beauty of this one, too, is that it will permit outside wheel to travel faster than the inside wheel when turning in a coast or neutral power condition just like an open diff. A weak link has been cited on some other drag racing forums about the bolts that secure the worm gears and it is recommended that they be upgraded to an alloy steel ARP bolt for improved reliability. I could imagine that towing could induce the same stresses as experienced on the strip. This is my second choice, with ARP bolts, of course.
The Detroit Locker uses teeth to lock the axels while under load – either accelerating or decelerating but releases when ‘coasting’ through a turn or while in a neutral power condition (neither accelerating nor decelerating) and temporarily acts like an open diff. There is an apparent clack when the teeth engage and disengage. I have only read in a magazine where someone knew this guy who’s buddy’s sister’s boyfriend fragged his Jeep’s Detroit Locker climbing this rock hill, etc, etc. The violent loading and unloading of some crawling could strain it enough to break but most likely the axel will pop first.
My point is that this unit has been the common standard by which to measure locker durability and performance for decades. The long wheelbase of the Excursion will help tame the locking and unlocking that causes some of those lifted CJs out there to do emergency lane changes in the corners. This is my first choice for a diff upgrade for my 05 Excursion.
Generally speaking, I prefer the low tech and KISS philosophy.
Comments expected and welcomed. (And need some back up on the Tru Trac)