Transmission?

here goes...automatic steptronic transmission never had any problems, now ONLY from Park to Reverse will it make a distinct CLUNK noise... sometimes...about 1 out of 10 , not sure if its the Tranny, selector cable, drive train, or Diff. fluid lvl looks good...fluid looks good...advice?, besides "go to a dealer"
Transmission?
Check the mounts
Transmission?
check your ATF level