No traction at all and rear end question

[allen123]

Alright my truck gets no traction what so ever. It has brand new 295/50's on the back but when its raining if i barely hit the gas the tires just break loose and i have to let off the gas completly because once they start spinning you cant feather out the throttle to stop it, you have to let off and let it stop.

And also i've asked before but does anyone know why my truck will sometimes posi up and sometimes do a peg leg?
Like everytime i leave school we all get on it and mine everytime will spin them both and throw me sideways but other times it will just do one side, and everytime when it rains it will spin them both, and it spins both in reverse. It is a 12 bolt but thats all i know about.

Just wondering if anyone would know.
thanks!