Detroit lockers are weird. Very sloppy auto lockers that will do weird things when you're at pucker factor 5. Anything other than dirt you need to learn how it drives.
There are carbon fiber clutch plates available along with some tricks like building them with extra frictions to tighten them up, but they give up the ghost a little earlier than expected
Careful. The pre-load in a clutch posi, especially a tight/grippy one, can bite you on slick surfaces. When you lift the throttle, both tires still want to go the same speed. OTOH, an auto locker disengages when lift the throttle.
Old Detroit's tended to be sloppy. Newer design is better. Powertrax no-slip doesn't have slop either.