1970 340 Balance Problem...Bottom Line

hi. is the vibration there at a higher speed too? yes your torque converter has small balancing weights. have you changed your torque converter lately? did you look at the flywheel for cracks in between the bolts? if there are cracks you will have a vibration as soon as you rev up because the flywheel will ot be running true. take your torque bolts out of converter and slide the converter back. now start the engine and see if he vibration is still there,if it is gone I would look at the torque converter an check the flywheel. hope this was helpful.