Are you sure its the trany jumping and not the engine? The engine can rev fine in neutral, but in gear (under a load) it can miss and you will feel it jumping. 2500rpm,s is def a load. Its kinda like setting the timing, the engine may sound fine at idle but when you drive it under a load, thats when you find out if its right or not. Im not saying its your engine, but it is a good posibility, are the plugs and wires in good shape. A bad O2 sensor will cause it to jump around also.