I would go back to the place where you had your tranny replaced and explain it to them, then make sure they can pin-point the problem. Don't take any guessing from them, that would just mean the possiblity of them to start throwing parts and money to try and fix the problem.
I just wasted my time and money on a wheel bearing that did not need to be replaced. I made the wrong assumption and paid the price for it... worse the problem on my van is still there and I can not make sure where the problem is. Would like to take it in for a diagnose, but now I'm short on cash and don't know any good thrustworthy mechanics on my side of town.