So i recently installed the new 440 and i took it out but when i bring the car to around 1800 - 2000 i get a horrible driveline vibration and it smooths a little more as the rpms climb. The motor ran fine before in the gtx it was in however the only thing i have changed is the stall/convertor. I have checked the harrmonic balancer as that is what it felt like however it is good. Anyone had this problem before any suggestions. Also i have checked the flexplate to flywhell/convertor bolts all are tight. Thanks in advance!

Wrong converter? You need to see if has weights on it or not. Then figure ouy if your engine is internally or exturnally balanced.

motor is and internally balanced 440 70 model all new with around 1350 miles on it

Does the converter have weights on it?

just checked yes the convertor has weights on it

take the weight off it. weights are for externally balance engines. IE: 360, 440 cast crank engines, most 400's, and late 340's. Your engine should not have a weighted converter.

thanks for the help i will remove them tommorow and post an update

Vibration is gone sorry for the late reply. Thanks again moparts members!!!

weighted torque convertor took the weights of vibration free

Glad you found it and it wasn't too hard to cure.