track lock is a limited slip like chevies posi or mopars truelock when in snow and spinning your tires both tires should spin, but if going arounda corner one spins faster tahn the other so you dont "bark" like you would with a full spool.
new ford trac locks work great. (at least my experience). while i dont rock crawl and have one tire in the air a lot they've always worked good in snow and mud for me. A trac lock IS a limited slip. is your one tire vibrating on pavement or mud. when mine was about to blow up it vibrated.