flushing transmission, help please

[apowers2k]

whats up everyone, i have a 02 gt with about 9500 miles on it, the tranny for the past 2 months has been bumpy with it kicking back and forth before it shifts like on mostly 3rd or 4th gear if i let go of the accelerator, and if i let go after it shifts it also kicks back and forth roughly, its just been rough ride as of late. i thought about doing a tranny flush, to see if maybe it would clean out the tranny of any left over oil or dirt that might be building up there. i went to one shop already and they told me that by the doing the flush, it might make the problem worse, is this true?? also is flushing the tranny then something good that i should try? any other suggestions would also be helpful please for what i can do. thanks again guys, take care