just recently got my car back up and running with all new front end suspension and k member... the problem i am having is as soon as the car goes into overdrive or lockup i get a chattering and shuddering at any speed or rpm in lockup... i feel it throughout the center of the car and its pretty bad... ive had it before with the previous motor. trans is a select built race unit with a 3600 lockup stall 10", spohn tunnel mounted tq arm, moser 12bolt rear with a detroit truetrac diff and 3:91 gears.. i believe the driveshaft was shortened and rebalanced and new u joints due to the aftermarket rear... i dont know what to check

any help is appreciated greatly

 

damn.. guess no one had a similar issue?