Vibration - not always wheel balance issue

[MYBAD79]

I had a very annoying vibration at 65mph, it was quiet violent when lifting off the gas pedal at 70mph and coasting to 60mph .... I figured I probably lost a balance weight so I didn't think it was a high priority to get taken care of, I don't drive the car that much .....
I just put over 100 miles on the 79 going to CocoaBeach and some US1 cruising .....going 75 on 528 I noticed the vibration is completely gone, runs smooth as silk .... Coasted a few times from 75 down to 60, no vibration whatsoever ....
Then I realized I just fixed the body mounts a few weeks ago, obviously crumbled body mounts can cause some really nasty vibration .... I would not have guessed .....

 

[Twin_Turbo]

Me neither unless the body was loose on there and a small vibration was greatly exaggerated by the loose body.

 

[MYBAD79]

Me neither unless the body was loose on there and a small vibration was greatly exaggerated by the loose body.

I begin to believe the dropped body changed the angle of the steering column enough to cause a problem.... the front two mounts were shot so the body sat almost an inch low putting a bending moment on the rag joint ... might be a far stretch but the steering box is bolted to the frame, the steering column is bolted to the body.....

other than that I have not come up with any better explanation.....

 

[mrvette]

Me neither unless the body was loose on there and a small vibration was greatly exaggerated by the loose body.

I begin to believe the dropped body changed the angle of the steering column enough to cause a problem.... the front two mounts were shot so the body sat almost an inch low putting a bending moment on the rag joint ... might be a far stretch but the steering box is bolted to the frame, the steering column is bolted to the body.....

other than that I have not come up with any better explanation.....

Shit!!! now you all gave me another project to mess with, I not looked at the aluminum pucks on my '72 for some maybe 15 years now.....:flash::devil:

back when replacing #4 mounts, been a while....

:suspicious:

 

[DeeVeeEight]

Crumbled, rotted body mounts means metal on metal, or fiberglass on metal, to me. What puzzles me is the decelleration (sp?) contributing to the vibration. I would have thought it would be present more often.

 

[mrvette]

Crumbled, rotted body mounts means metal on metal, or fiberglass on metal, to me. What puzzles me is the decelleration (sp?) contributing to the vibration. I would have thought it would be present more often.

EH, your exhaust is too quite, or you have a sensitive ass.....:crutches::flash::devil: