Shake, Rattle and Roll.

I am new to the FORD/MERC scene, and my Comet is also a new addition to my driveway, so I'm still learning. I have a vibration issue I'm trying to sort out that is always kinda there but is worse in the 30-50mph range. Shakes the steering wheel, the dash and it is felt throughout the car. I have new front brake calipers, new tires, and just got them balanced on the inside and outside of the wheels (American Racing alloys). That helped some, but its still a problem. There is no noticable front steering/suspension slop or clunks, aside from a slight drift to the right when initially braking. While coasting in neutral I turned the key off and the vibration didn't seem to change at all, so I think I can rule out the drivetrain as the culprit. I am having the rear frame rails replaced soon because they are rusty in the back where they connect to the shackles, and maybe that could be causing some issues I'm guesssing, but I don't know much about that. Any ideas?

 

Driveshaft out of balance, Ujoints worn

 

That was one of my thoughts, but figured the vibration would change or stop completely once.o threw it.into neutral and turned the engine off while.driving at 40mph. Would unbalanced driveshaft or worn u joints still be noticable with the engine off and rolling in neutral?

 

The driveshaft is still rotating while coasting in neutral, so you cannot rule that out. What you ruled out was the engine and possibly the converter.

I would inspect the u-joints first.

 

Before removing driveshaft parts, cant I jack up my comet, support it with jack stands, and bring it to speed, then visually inspect the driveshaft and axle movement to see if the vibration is detectable?

 

Yes you can...

 

I wud remove the shaft, have it tested for balance or that it's not bent. Removing the shaft is not that big of a deal. If u do the test mentioned and find out it's unbalanced u still will/shud have it professionally done. I think that's a bit safer than running a car 65mph on jackstands. I had a similair issue - mine was unbalanced and slightly bent. JMO

 

Thanks all! I will investigate and post the results.

 

Bueller!

Sorry, first thing that came to mind.

 

Sometimes, the u-joints are so worn out, that you can tightly grab the driveshaft, near the u-joint, and shake it. If you can move it "at all", replace both u-joints while you have it out. It definately sounds like a u-joint/driveshaft problem. If your driveshaft is warped, you will have to replace it.

 

Lol!! Oh no, I replaced the Bueller Ferrari with my Comet "in my mind" for a second. Thank god I switched it back before it fell of the jacks and launched out the window.

 

I'll definately get under there and check things out before I start leaving key parts behind me as I drive.

 

I have magnets on my drive shaft from the aftermarket cruise control speed sensor. Would that extra weight cause my drive shaft to be unbalanced? Especially because it can be moved by hand a little left and right. I have a vibration and am investigating that.now, but never considered the magnet weight. Any idea??

 

I had a similar problem last summer. Ended up one of the rear shocks had a broken upper bolt and wasn't controlling the leaf spring. The spring would oscillate and shake the whole car.

 

the magnets can be the cause. remove them and see if that makes a difference.