I changed the seals on my 2002 379. Dont adjust anything, your truck will leak water in the cab. I have to slam my doors too. The issue is, there doesnt seem to be any type of check valve anywhere in cab so now what you are experiencing is cabin pressure with the doors closed. IF i crack my window an inch, the door will shut just fine with no slamming. So try that. The seals do wear in with some time.