2008 Yukon Denali XL with around 160,000 on the clock. Often when shifting (usually when downshifting when getting on the throttle to pass on the freeway or when giving it throttle after slowing down) there is an audible and felt “thunk” as if it is being slammed into gear. Sometimes it does it cold when up shifting from 2nd to 3rd but it only does it cold. After that the clunk is usually felt when getting on the throttle. Tranny fluid was recently changed at the dealership and nothing strange was noted. It has been doing this for a long time. Any ideas what could be causing this?