Ok I got a 2004 Silverado 5.3 regular cab. I have not had any problems with the transmission since I had it. The RPM gauge has been out since I had it, also during the day you can't see PRND321 but at night it is illuminated. Ok I had a set of 20 inch wheels put on my truck. Drove duck hunting come home. Finished putting cd player in my truck. Went to leave to go see my parents and when I put the truck in drive it seemed to have no power taking off. I knew something wasnt right so I stopped cut the truck off and cranked it, made sure I had it in drive then took off again and just took off like it was sick. Well I went on to my parents thinking that it might change and maybe I was just worrying too much. Well got going good and it shifted fine into all gears but would not go into overdrive. I knew something was def wrong. I stopped at end of road and put it in 1st and so on an so forth an it does not slip a bit manually shifting it. But if you take off in drive it is like it starts out in 3rd gear or something and has no power. Well took it to transmission shop and the main guy was out and the one working did not have much experience but I had him hook it up to tester. He said all the sensors tested good. He drove it and said he thought it was the valve body or something in it. I took pan off looked at oil was no metal shavings or anything to be concerned about or anything on magnet. There was a little gunk in bottom like from where the fluid needed to be replaced maybe I dont know. I put new fluid back in, new filter and put it all back on. I had my check engine light codes ran at autozone and had 9 codes and all was transmission codes. All said something about selenoids or could be some type of fuse or something electronically. If anyone knows anything about this I would appreciate any help or advice. I was told that I should have had my truck calorbrated for the 20 in rims at dealer but I think the transmission messing up a day after I put rims on to be a coincidence. I know many friends that have 20 inch wheels or bigger and never got there truck calorbrated. I am in college and need my truck fixed asap. Please help!!!