Ive got a 1999 tahoe that has recently been having some problems shifting. Like a fool ive beaten up the truck a bit from work (running to get parts and stuff). I was going to race around someone when i noticed the truck would not go past 60 and i was at 4 or 5k rpm's and i heard a rattling noise. Since then ive noticed that if i get on it the same problem happens, at any speed. (so in between any gear) and the rattling noise happens again. the tahoe seems to drive fine, shifting gears normally if im easy on the gas.

Im trying to get a last minute, end of summer, road trip in with a couple of friends, so any advice on what could be wrong would be great!