I have an 88 4.0 auto sometimes when I shift to reverse the jeep just revs as if its in neutral. after a couple of good revs it will jump into reverse. also going down the freeway it will feel like it looses drive and now is in neutral and the engine just revs. after this happens when I sift it to 3rd it goes to second any ideas I already changed the tps a few months ago for an erratic shifting problem