Pretty weird: tranny shifts absolutely perfect until it gets good and hot.
Drive about 10 miles or so, and the 3-4 shift gets a bit soft, then goes away completely. Can sometimes rev it to 4k in third and back totally off, and it'll go to 4th, but then shifts back to 3rd for no reason.

Continue to drive, and it'll lose third also, and just shift down to 2nd for no reason, and not go back up to 3rd.

Let it cool down and it's perfect again.

checked all the usual stuff, cable mod, etc. Of course fluid is just right and very clean. Trans is not overheating. drove several miles at 25 MPH in 2nd and it was only 200 degrees, same as engine.

I suspect it's some little hing, probably in the valve body; since it works so flawlessly for several miles before it gets totally warmed up.

Tks,
DG