Are you sure it's from the tranny? It sounds like it could be a bad wheel bearing. If it is actually from the tranny, have you checked / changed your tranny fluid lately?
I was going to have the mechanic change the fluid (had it done at 60K now at 74K) but he didn't know how many quarts to put in. I was in Yosemite Natl Park and it wasn't the most confidence instilling place (but nice).
Would a wheel bearing make noise only going uphill?
Hopefully fluid makes the diff. Have you heard anything about Saturn fluid making the transmission noise go away?