I have a 1986 Lincoln Town Car with 151,000 miles. It has developed a vibration that I’m pretty sure is coming from the rear. Up to 45 mph its O.K… Then as I go from 45 to 50, the vibration starts and gets worse as I get to 50. From 50 to 55 the vibration dies away. I do not get it on new, smooth blacktop roads or on smooth concrete bridges. I have had the front of the car checked, looks O.K… I just had new U-joints put in, and it actually got somewhat WORSE! Could the driveshaft need balancing. The slip yoke is good, I looked at the 4 control arms, the rubber bushings and the shocks. They all appear good, nothing is leaking, no shiny metal anywhere, no bleeding shocks, no cracked welds at attachment point. The tires do not have excess play.

Does anyone have any thoughts. Ever need to balance a driveshaft before? Thanks very much, Bob

This is Bob again. Forgot to mention that I had all 4 tires re-balanced. The right rear was replaced, bulging sidewall on both sides of tire.

You don’t seem to be getting much action here. Try or

The best possibilities I can think of are springs or shocks. Most of the Town Cars and Vics I see still running around have weak, sagging springs and worn shocks. Badly sagging springs can cause the angle of the driveshaft to be too great, resulting in a vibration. Worn springs and shocks can amplify this on rough surfaces. Look at the way the car sits, and if it looks like it’s sagging in the back, replace the springs and, preferably, the shocks too. They can be worn without leaking. In case you have a skewed perspective of what is normal with your car, you may want an unbiased party to look at your car and tell you if it looks like it’s sagging in the rear.

I would like to see your tyres rotated. Get the tyres on the front to the back and the ones on the back to the front. If there is no change in the way it feels that should rule out wheels and tyres. (BTW for safety, the best two tyres should be on the front and there should not be a large difference in wear or tyre type from side to side.

I don’t believe this is the most likely problem but it an easy-cheap one to test.

Yes, this will be my next step.
Thank You very much.

This is really good information and makes a lot of sense, it all adds up. This will be my next step after tire rotation. I replaced all 4 shocks 1-1/2 years ago. Thank you very much.