A833 Can't Downshift / Poor Performance

I'll be the first to admit I know very little but you did NOT mention if you verified bellhousing bore alignment with a dial indicator. Seems to me that if the input shaft is off center, it may be getting enough side loading not allowing it to stop rotating.

I've only rebuilt one 833 and haven't installed it yet, but I'm counting on it working because it's registered for Carlisle.