Trans clunk, R to P, after service and new pan.
 

So, i did a trans service last week, replaced my stock pan with new Dorman pan because it has a drain plug. Took out 6 qts, put in 6 new qts of atf+4, and napa filter. I put the magnet around the drain plug nut and the magnet now sits a little higher in the pan, maybe 1/4 inch higher. Problem in having is there's a loud clunk when I shift from reverse to park. Doesn't sound like a mount, I'd swear something is hitting the pan. I just ordered a new Mopar filter, am about to do the service again and put the old pan back on, and see what happens, unless someone has some other explanation.

Dorman pan?
 

Well, I don't know for sure what caused the noise but...I did another trans service today, removed the Dorman pan and Napa filter, installed new Mopar filter and gasket, cleaned up the old pan and reinstalled it and poured in 6 qts of Mopar ATF+4 and the noise is gone. If I didn't know better, I'd swear it's shifting smoother now too.

That is an odd one, but hey, weird things happen sometimes, you know? I was going to suggest you look for exhaust system component contact with body/frame/other when the drive-line rebounds on R-P shift because it happened to me three times. The first was due to a broken tranny tail-mount, the second due to aftermarket header clearance on a 4.0L (thunked or rattle-rumbled, load-dependent) and then there was that pin on the front-pipe... but hey, good find! Nice going and good luck!