I have a 1966 mustang that has a vibration when I let off the gas and slightly through the range. I have done an alignment tire balancing. And I know before I got it the previous owner had the back u joint break going down the road. So I suspect the drive shaft is to blame. I am just wanting opinions on my diagnosis before I take the shaft out and send it in for balancing any other opinions?

 

Ujoints is where i would look first, then i would look at anything after that, part of the rotating assembly. A warped or worn brake rotor can through it off to.

But the way you describe it , it sounds like the driveshaft. Crawl under the car and check for any play in the ujoints, if its good, then you may need to bring it to a tranny shop to see if its balanced.

 

When I got it I had to reinstall the driveline so the u joints are new since I did both instead of one. It has drum brakes if the drum was warped instead of the rotor since I don't have one would that be the same result?

 

same result, its a rotational mass that is spinning anything that is out of balance will result in a vibration.

 

It sounds like a driveline vibration. First step Visual inspection... Just look for obvious wheel weights missing, bent rim, deformities in the tire... U joints integrity. Missing driveshaft weights ... If nothing seems obvious next is determine if it is speed related or Engine RPM related... Does the vibration occur approx the same rpm in each gear or at a specific mph (hub/ rotors.. Rim/tires)....If it RPM related focus towards the driveline... More than likely the driveshaft like stated previously. Good Luck