What tranny? I have a t-5
I am dealing with a similiar situation and I don't know enough about trannys to know if my end play is okay or not. I'm going to take it to a tranny shop and have them look at it.
As far as other possibilties, you said you looked under neath your car, I hope that was with wrench in hand. Not preaching here, but I just got egg in my face like Dan did because I found out a clunk was caused by a loose diff mounting bolt. Couldn't tell by looking, but it was almost two turns loose-and it made a lot of noise.
Keep us updated.