I know there have been similar threads on this issue, but I think mine is a little different. Yesterday I was backing out of a parking spot on level ground and the shift from park to reverse was pretty harsh. I put the truck back into park and tried again, and it did the same thing. I did it a third time, same result. I then tried driving forward a bit, came to a complete stop, and shifted to reverse. Same hard shift.
I took a video that I will try to post, but I'm not sure it does it justice. Make sure you turn your volume up.

2019 5.0 4x4 with just under 16k miles. Outside temperature was lows 70s.

The truck has never shifted this violently into reverse before, even with a cold engine in below zero temps.

Any idea what's going on here, and should I be concerned?

 

My 2018 3.5 did what you describe one time. It was harsh going in reverse and drive. It consistently occurred as I experimented like you did. I turned off my engine and parked it thinking something is broke and was planning to take to dealer on Monday. Next day I started truck and couldn’t duplicate. Then decided to put vehicle in 4x4 low. The harsh reverse and drive felt the same when in 4x4 low. Go to 4x2 and all seems normal. It never happened again. Try 4x4 low and see if harsh shift into reverse is what you experienced.

 

I find it does it if you do not wait for the RPM to lower after starting.

 

Although I can’t prove it, i believe my truck somehow thought it was in 4x4 low and caused my abrupt reverse. Since it never happened again I’m not worried about it.

 

My 2020 has done it a couple times. No rhyme or reason.

 

Mine has done what the OP'er has stated. Only a handful of times since I bought the truck 6 months ago. Seems like the gears don't mesh periodically or something.

 

this is why

 

Thanks for the responses guys. Similar to your experiences, it hasn't happened again so far. I was all set to take it into the dealer but figured I better wait.

 

Now I remember I did take my 2018 to the dealership and told them of the problem I experienced and requested they perform the latest TSB related to transmission issues. There was a TSB for transmission shifting Problems that was for 2017 and 2018 manufactured vehicles. They installed it but I have no idea if the TSB corrected the harsh reverse but it never happened again.