I was dropping my 89 XJ off the trailer (in the snow) to get it into the garage to get some work done. Its been sitting in storage for 6 months. It was in 4 lo and I was reversing off the trailer. As the back tires dropped off the trailer all power to the ground was lost. Jeep (AW4) felt like it was in Neutral. Moved the shifter to each gear (1-2, 3, D, N, P) and there was no engagement in any of them. Ended dragging the trailer out from under the Jeep just to get it off the trailer. Got back in the jeep and the transmission will not shift into any gear. I tried changing the transfer case to 4hi and 2wd but still nothing. Any ideas on where to start the trouble shooting?