M.B. DOC; that lock up thing sounds like what happened to mine. Transmission was working perfectly until I backed up and I shifted to forward but it never released reverse. I didn't realize it at the time but it was pulling forward and backward at the same time. It didn't take long before it burned up, so now I have to buy a rebuilt. Had I known what was going on in there I probably could have saved it. I only had to "walk" 63 miles to get home.