The TrueTrac uses gears, not clutch plates for it's limited slip action. It is not prone to wear and it doesn't require any special gear oil additives like the clutch type diffs do. I really liked mine (front) in snow, ice and mud. It has one advantage over lockers in that it can sense the torque to each wheel and adjust the torque bias before a wheel slips. For example when turning, an auto locker lets the outside wheel
"freewheel" since it is over-running the ring gear. So all the torqu goes to the inside tire until it slips at which point the outside wheel locks up and you get torque to both wheels (with the inside wheel slipping). With a torsen-type diff, like the TT, both wheels get torque in proportion to their traction. So as long as you don't overpower the tires and make both spin, you end up with both tires pulling and not slipping.

This really helps on off-camber situations where a locker tends to let it's tires slip to the downhill side. I recall a few times on a muddy sidehill having the Detroit-locked rear end slding down the slope but the TT front end was pulling straight ahead. So ended up crossing the slope with the front wheels pointing where I wanted to go and the rear end angled down slope with the tires churning along sideways sort of like this