Detroit locker posi unit??

Hey thanks so far guys for the good info. Here is where my problem is. On a stout motor with the 4 spd. It has enough slack that when dropping the hammer on it with that slop, It is putting alot of unneccesary twist on my driveshaft, pinion gear, etc. You can actually feel it pull right going thru the gear box under hard acceleration. It feels like the driver side axle is broken, yet it will lay "posi's" down on the road with the radial drag tires. The rear suspension is fine. I thought that was the problem at first, and have just put the new Caltracs in with mono leafs and shocks and new calvert spring perches, and the problem is still there.