slow chev

so ive got an 02 silverado 5.3 Z71 4wd and every once in a while it makes a clank then jerks it feels like its in the front end but i cant pin point it the rear end was brand new a year ago with a tru trac and everything else new the tranny was put in 3 years ago and it dont have 20 thousand on it but i just had the motor out cammed it and put a circle d 3000 stall in so i dont know if its possible the converters stayin locked up then comin unlocked i have no clue but it does it just cruisin or comin down off a hard pull but not always didnt know if anybodys had this problem before thanks