Hard Drive to Park shift

[K20Submarine]

Alright so weather permitted I was able to go outside and check the mounts and most of the drive train for play. I couldn't really find anything that moved around a lot, the tranny mounts moved slightly but they are large black rubber things that look like they are intended to take a little shock. Now heres what I found shifting the truck with a little special touch. When I shift from Park to Drive and I do it quickly and not stomping on the brake the shift is pretty clean no thumps or jerks, but if I hold the brake pedal to the floor the shifting is much harder, can anyone make any sense of this? Thanks for quick reply earlier Orange.