my truck has only 1500 miles and i can not get a clean shift from 1st to 2nd while towing, especially on a hill. it seems to clunk or grind going into second. when i picked the truck up at the dealer , i could not get it out of reverse in the parking lot. when i did , i tried it again, and it was very hard to get out. after about 10 times , it works pretty smooth and does not get stuck. i put about 300 k on 2 nv5600's and never had a problem. i do not think it is me. it seems you have to let the rpms drop with the cluth in before you go to second and not rush the shift and everything is smooth. the problem is when your towing up a hill , then second is almost no good anymore.