I've encountered a harsh shift from 1-2 and especially while going uphill, when shifting from 2-3 it acts like it tries to slip into 3 prematurely and happens under partial throttle and especially under full. I've changed the fluid and filter no contamination refilled with the correct GM fluid and have no codes set. I've heard that these 4l60's have had a problem with shifting and do they make a improver kit to help this problem or is there another issue elsewhere? Thanks again for any replies! Chuck BTW when I search 4l60e, nothing comes up???