Any help would be greatly appreciated. What could be causing this?

No slips or anything, however when I am accelerating then all of a sudden let off the gas, the transmission down shifts hard. I can prevent this from happening by easing the gas off slow. Does this sound like my tranny may be going bad? Fluid level is good. Doesn't seem to be discolored or smell too bad. There is also a whine in 1st gear. Two mechanics told me it is a "normal" Ram whine. It gets louder as RPMS go up but quits after switching to 2nd.

Can U joints cause this (downshift issue)? If so which one?
I just bought the truck so I'm not sure if atf fluid/filter has ever been changed. I thought about replacing filter but have seen mixed reviews. Thoughts?
Thanks for your time.

 

If you don't know the last time it was done, have it done. Fluid, filter, and band adjustment. See if that doesn't improve its attitude any.

 

I will do that and update. Thanks