Transmission shifting issue

My transmission on my truck has been acting extremely odd. It jolts, sometimes very hard and other times it's hardly noticeable. Always seems to happen around the 2,500 rpm range and also seems to be more pronounced when downshifting to go up a hill. I've had the transmission flushed and the mechanic said there was quite a bit of fine material in the fluid. Don't know if this could be residual material clogging the solenoids or if I'm going to need to get the transmission overhauled. I haven't had a check engine light come on throughout this entire time. Thanks