So I've searched and read here and other sources... no problems seem to mimic mine, so here goes:
I have ~95k on my OB... had it about a yr (~25k miles put on in that time)
Occasionally, un-related to operating temp, I get VERY hard shifts... BANGS into each gear, and downshifts hard as well.
It goes away after a few minutes, and will be fine, sometimes for days.
The other day, during one of these 'episodes' I switched to "Sport" mode, and attempted to upshift manually, since it was also shifting at higher RPM points than normal (not in "Sport" at this time)
Well... It would not allow an upshift from 3rd to 4th, despite turning 4 grand+, at over 45-50 mph... the upshift arrow would not light!