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!