vibration issue

Dana67Dart said

Things I think I remember...

The hole in the end of the crank on some engines is different diameter then others. The torque converter front nose must match.

Some engines are externally balanced and the balance is on the torque converter

Some engines use a externally balanced front dampener.

Vibration in neutral at 3000 rpm or only while in gear?

Vibration at 3000 rpm in park?

Click to expand...

All 340's up to 72 were internally balanced. That is my understanding. Won't know about the hole and torque converter nose until I drop the tranni. Flex plate bolts up easily. I believe it is the original. The vibration is present whether in neutral or park. Mostly noticeable while driving under load at specific rpm. You can feel it in the seat of your pants and see it in the rear view mirror.