what is your gear ratio in the rear axle you just may be at too low RPM, its possible anyway or you may just be hitting ice and then pavement on the incline. does this happen on any incline or just this one? if its just that one try another incline and see what happens.
on any incline, no ice on the road, If I keep my speed up Like 70 run fine I like going the speed limit,gear ratio? It is a stock truck from ford I think they would put the right rear end in but never know .