Reverse Clunk

[Suzuki6mx]

shift from drive to reverse CLUNK real loud.. Automatic

[Eastendlou]

If you have an automatic and you select reverse or drive or whatever then feel/ hear a "thunk" it could be the U-joint. Other symptoms are vibrations at hwy speeds. My guess is universal joint or maybe a motor mount. Replacement or adjustment.
I'd have a tech look at u-joint, rear diff, motor mounts and whole tranny. Don't let it go too long or it could leave you stranded.

If that sucker comes apart at hwy speeds your F'D in the A.

[jth111]

Check the spline where the two piece drive shaft meet. There is a bearing in there that gets dirty and looses the grease. I had the same problem and I took it to the ford dealer and they took the spline apart cleaned it and re-greased it with a special grease. It solved the problem. I thought it might be the u joint but it was just this clean and re-grease process. I was amazed. I now have no problems with that. I have 157k miles on this original engine and tranny. I hope that will help.