Currie's folks say a well-prepped trac-loc can stand up to quite a bit of abuse. Stock ones have a weak point in the cast cover over the clutch pack. So everyone (Currie, Randy's Ring and Pinion, etc.) makes billet covers. Currie said, "When you put that
kind of power to a stock trac lock the cover flexes a lot causing it to
crack around the ring gear bolts, and causing the clutch discs to only be
grabbing on the edges because the rest of the clutch contact surface is
flexing out of the way so it doesn't even get used. You also have to realize
that the trac lock will work for this application (my fastback), however the more
horsepower and torque you put to it, and the more you improve your traction,
the shorter the lifespan of the clutch pack gets." So, short answer is the modified trac-loc doesn't suck, but the DL is more burly.