Clunk when shifting and towing

So just finished a long 800km trip towing a ~3500lb tt.
Recently changed all fluids, greased u joints and drive shaft splines (Motorcraft spline grease stuff).
Changing gears from 5 to 4 (mostly) I often get a loud clunk, which I can ease by either very slowly and carefully downshift, or shift fast and hard.
I’m thinking I may need to adjust the clutch (very little play). But reading another post it could be my damned carrier bearing again?
Any help and hints would be appreciated.
Carrier bearing was last changed <10k km ago, gave me grief while towing my tt.
Truck’s lifted 2“ on blocks.
Thanks to all.

 

Just cuz the ujoints are greased doesnt mean they are good...

 

Ah yes, good point. What the best way to check those? Just look for play?