<VV> VV Low speed shake .

[John Miller]

I have an early model w/PG. on low speed take off forward, the car has a very profound shake almost like driving on a blown tire.(tires are 6 months old)
 Pop it in reverse and it does not shake whatsoever. I pulled drivetrain and replaced torque convertor and transmission. While there looked over diff and axles, saw nothing out of ordinary. Jack the car up and let it run, it makes no unusual sounds. Only on the ground and traveling forward under 10mph. Ideas on things to look for?
 John Miller