[steeeeeve]

thanks for all this info guys. i will check the suggestions and look for witness marks.

more info on the truck

new 350 from jegs installed last year
rebuilt 700r4 installed a few month ago from a reputable trans shop
new driveshaft/u-joints (converted to 1 piece during trans swap)
truck is bagged
new tucked exhaust as of about a week ago. shorty hedman headers.

i've noticed it make the rumble if my foot is just slightly on the gas pedal at cruising speed. just a touch more and it goes away.

then during slow speed acceleration i think i can feel the rumble in that sweet spot for just a short instant.