BIG BAD VIBRATION

[Gary 30U]

As some of you know I have been fighting a bad vibration now for several years. This may take a little space, but I think it is important to tell the whole story.
When  I first got my car going (about 6 years ago), it had a bad vibration. This vibration was related to the engine RPM only. I was not affected by speed, road conditions etc. In fact you would get a bad vibration if you were setting still and revved the engine. The vibration occurred while the engine was in compression and slowing. While decelerating from 35 to 25 mile per hour it would nearly shake the car apart.

I did all kinds of things, checked timing, (had the distributor rebuilt, as it had a loose shaft), checked for anything solidly connected from the engine to body or frame (I did find a couple minor things), found the front motor mount was bad and replaced it. STILL NO  CHANGE IN VIBRATION Thought the front motor mount was it as it was bolted direct though to the frame.

I thought if the front motor mount was bad, well what about the rear ones. Sure enough the one had delaminated itself and the inside plate was sitting on the frame. I had an extra set of plates, so I took them in to a company here in Oregon and had them re-vulcanized. I took out the old motor mounts and replaced them with the rebuilt ones. STILL HAD THE VIBRATION

Over the last few years I have tried anything anyone suggested.

I took the car to a Cruise-In up the Columbia River gorge last Saturday, (about 100 miles each way) and said this is enough, I have to fix these rattles. Well after I got started I figured I would try to fix the vibration which caused the rattles.

One of the fellows in our Tech Committee had suggested that maybe the new rear motor mounts were bad. I had kind of dismissed that idea, as they were new.

If you know how the rear mounts are constructed they have a 1/2" rubber sheet vulcanized between two steel plates that have 4 carriage bolts sticking out each side for mounting to the frame and the motor. Well I took out one of the motor mounts today, and sure enough if was bad. Using an ohm meter I found that two of the heads of the carriage bolts hidden in the rubber were in fact touching.

As it so happens I had another set of motor mounts and was able to replace that one with a good one.

I took out the other side mount and it tested OK, but I replaced it anyway.

GUESS WHAT. I took it for a test drive and it was like a completely different car. NO VIBRATION

After so many years of fighting it, I think I finally won.

The moral to this story is simple. Just because you just replaced it, doesn't mean it can't be BAD.

Just something to think about,

Happy Motoring, Gary R.

[chetbrz]

Amen !!!

[frankp]

Can't trust nothin'

[ski]

good info!

[29plycoop]

Thanks for the follow-up. Will take a second look at my rear mounts. The front mount was revulcanized and works great but not sure of the condition on the rears. Nice looking car.

[racertb]

Good information to know...are these mounts available anywhere or is this an R&R piece?

[Tinkeys]

I think I have a pair or remanafactured 30u mounts somewhere in my shed if anyone needs them !