I have had a mechanic drive it.He checked out all the suspension,motor mounts.Rebalanced drive shaft and new shocks.He said convertibles are more prone to certain vibration ranges .He said it is the nature of the convertible frame.He said your dealing with a car built with 1960s technology.Also the car is more prone to body flexing more so than a hardtop of fastback.He explained that it is normal for vintage Mustangs and there is nothing wrong mechanically with the car.He said you are experiencing cowl shake .He explained new tires are not perfectly round and being a convertible is more prone to imperfect shaking.Gm experienced the same problem with the Camaro shaking at at the same speed.GM added cocktail shakers as they call it to dampen the vibration in convertibles.

 

Thanks for the info!

 

You lucky.If you search Internet .There are so many articles about this 50 mph shake as the gentleman mentioned about his 67 convert.You have to remember these cars are 50 years old.More vibration than new cars.Heck the steering column is directly bolted to the suspension.No dampener.I believe you don't have a vibration I have owned two 68 Mustangs convertibles Restored all the suspension.Tried several tires.Never wrecked.Both vibrated at 50 mph.It is the nature of the convertible frame.Also the tires picking irregularities in the road.Had the drive shaft speed balanced.No difference.Taking a Ford Falcon frame and turning it into convertible is not an ultra smooth car.If you have never heard of cowl shake .There are many internet sites that give you the definition as well as others complaining about this problem.You have experienced cowl shake.Ever drive your car and hit a pot hole and the front end shakes.Cowl shake.Drive a hardtop or fastback do not flex because of the ridgity of the hard top when hitting bumps on the road.I am referring to convertibles only.I read an article on another site.65 Mustang convertible shaking at 50 mph. All new suspension brakes ,etc Another gentleman replied.Owned my 67 convertible 38 years.50 mph shake.He stated it ain't going away.I love my Mustang and I just stay out of that speed range.A gentleman who owned a 1967 Camaro convertible.50 mph shimmy.Gm tried to fix the problem by installing canisters on all 4 point on the car to smooth out vibration Canisters meant to absorb vibration.Convertibles are just more prone to vehicle flexing.I have ridden in Mustang Hardtops fast backs from 65 to 69. You can feel that they are much more ridgid.

 

I have a 16 mustang v6. Vibrated its *** off I noticed on day one. Same drivetrain vibration alotta people have...it was very bad initially. Under warranty per a service bulletin they attempted to balance the d shaft and after that didnt help the dealership replaced the shaft with a new shaft. It was bbout 50 percent better but not gone. Second service visit I insisted they call ford hotline which they did. Hotline advised them to replace the rear axle assembly. They did. fixed!!!!!! It sucks i had to go through this bs but wanted to share what fixed it! Cars perfect now, Great car now I can focus on a few Mods.

 

no one bothered to check wheel runout?