1990 FULL SIZE BLAZER.I HAVE A GROWL IN THE DRIVETRAIN WHEN THE TORK IS ON. LET UP ON THE GAS AND IN GOES AWAY. REPLACED DRIVE SHAFT, U-JOINTS, NEW DIFF. REWORKED THE SPRINGS. DO YOU HAVE ANY IDEAS? THANKS

 

torque converter goin bad possibly, if its 4 wheel drive it sounds like chain in transfer case may be gettin ready to go. either way it sounds like it is coming from somewhere with gears (tranny,transfer case, or rear end diff, but you say you installed a new diff. and u joints). when you are on the gas they are torqued up and when you left off gas pressure releases, so a bearing or a gear is wearing funny and making noise when force is applied to it.