i was out cruisin woodward last night and thats when it started. i have an automatic 4l60e with the B&M trans pak. iv had it in there for about a year now with no problems. now it shifts WAY HARDER into 2nd and you feel a shake..kinda like you would if a mount was busted. i think thats only because i use the stock rubber mounts but their not torn. anyways i noticed that it only does it when the trans warms up...it has the right amount of fluid in it...i dunno what it could be!