If you are going to pull it, and still can't see anything wrong. Throw it in the back and take it to a local tech school and talk to the shop teacher. usually will give good free advise, trans shop too.
If I'm not mistaken, bellhousing forward you have to replace. Make sure it has an A body tailshaft. http://www.slantsix.org/articles/4-speeds/ODA833fourspeed1.htm
I'm tearing an 833OD apart right now myself. Did you put new gears in or reuse the originals. If they are originals, did you drive this transmission or is this a new swap.