okay so lately my trucks been acting weird. I have a 1999 Chevy Suburban K2500 with a 5.7 350. when I'm accelerating too quickly I guess, it shakes. this is what's been happening, I don't know how it started. I usually run the gears when I'm driving because I like going fast lol, well now if I'm in 2nd gear and hit 55-60 mph it'll start shaking if I'm applying gas, if I let off it doesn't shake at all but if I give it gas again it'll start to shake. then I have to let it slow down to about 50 or let it hit 3rd gear and it'll act normal again unless I jump up to 75mph. what is this? I bought U Joints today thinking maybe it was that but I'm not sure, has anyone else had this problem? I only have a cheap programmer on my truck but I don't think that's it. sound like a transmission problem? I have a small amount of play in my Differentials as well but I'm sure that's not it.