91.5 d 250 518 auto. It seems to get hung in 1st then when it does shift it will do the same thing in 2nd. The more throttle you give it the worse it is. If you don't let off it seems to shift back and forth. I'm talking mild throttle, the more weight the more it does it. Can't tell if it slips. But 3rd and up seem to be good. Truck is stock. Thanks