Greg
I have ex-ac-tly the same problem since 2 weeks.
It began when I was on a journey in Sardinia island in Alghero.
Air T raised to 100 F and the transmission shifted rough and whinning too.
I stop and wait for 30 minutes and all worked fine.
Anyway it seems this symtoms appears when fluid T is high particulary driving in hot T at low speed.
Any advices is welcome
Christophe Salvaing