New to forum. I have a 99 motorhome, with I think a 4R100.I had it rebuilt not to long ago for this same reason and the repair shop is giving me the run around. When I take off from a complete stop it revs like it did not down shift into first. It does not do this all the time. When I come to a stop, if I put it in first I can shift it manualy. I have even went as far as putting a new ECU(per the trany shop). Talked to another guy and he said it may be the speed sensor. Don't know if it is but the ABS light is on, but speedo works fine. Hope you guys can help me out.