I own a 04 2500hd, with 15,000 miles. I bought the truck rebuilt from a reputable man here in town. I love the truck and know the damage had or should have not had any effect on the engine/transmission. My question is part of the time when driving around town and the truck is downshifting at low speeds, it will shift very rough. Normally between 20-10 mph, I can feel a pulsating or jar in the brake pedal. It doesn't do this all the time, otherwise the truck is great. I had the filter and fluid changed by a reputable garage, but is still does the same thing. Any ideas? Thanks In Advance

What damage??

The truck is a rebuilt vehicle, it had the bumper pad, marker light, fender, and
door replaced, all on the passengers side, as well as some damage to the bed, so a new takeoff bed was put on. There was no damgae to frame, radiator, or anything else I could see or experience by driving the vehicle, only problem is the way the thing downshifts sometimes.

sounds like the adaptive shift to me.