I have 90k on my 00 Z and I had my transmission assembly replaced with a remanufactured one installed by the dealer under warranty at 46k. When I am on it, it shifts funny, with a little hesitation and a hard kick.....what is going on?

The warranty was for 36 months or 50k, I have now gone 42 months and 45k any advice on what could be the problem. It is time for a filter and fluid change but that can't be my problem.