Weird 47 vibration solution

[Old Henry]

I've been struggling with an increasing vibration in my drive line somewhere (engine to back wheels) for a couple of months. I'm thinking no one ever addressed such a vibration in quite this way.

When the vibration started a couple of months ago it was just between 50 and 60 mph. So, I tried to stay under or over that range. But, over time it got worse and started at 35 and never went away no matter how fast I went. It had symptoms of being in the engine (the engine alone vibrated at a certain high RPM) and in the driveline after the engine (it would go away if I pushed the clutch in or put it in neutral). It wasn't tire frequency so I knew it wasn't tires. The really weird thing was that, once in a while (very rare occasion), the vibration would be totally gone and everything as smooth as silk. The vibration was extremely annoying and lasted most or our 700 mile trip to the Tetons a couple of weeks ago except for one hour on the way home.

Just in case it was the U-joint needing lube I pumped a half cartridge of corn head grease in there while the car was running in first (that was a tight squeeze under there going down the road. Got a little road rash on my back) and pumped a bunch of regular grease in the middle driveshaft bearing at the same time. That helped some in that the vibration became more intermittent, only vibrating about half the time. Even that was an improvement over 95% of the time vibrating.

So, on the last leg of the 500 mile road trip Pepe and I just took to Capitol Reef National Park the last couple of days the vibration got real bad and I just sat there while driving and pondered, as I had been doing for a couple of months, "Why is the vibration intermittent? Why is it sometimes but not all the time?" Mostly I thought it was because something was loose and sometimes centered and not vibrating but other times off center and vibrating.

Then I had this thought: "I know the engine has a vibration at a certain RPM and the driveline also has a vibration. So, what if sometimes the two vibrations offset each other to make everything smooth and other times they accent each other to make it worse? So, why would they be "in sync" sometimes and "out of sync" other times? Maybe it's because of the way they're connected through the clutch! Maybe I could intentionally sync or un-sync them with the clutch!!" So, I tried it. I bounced my left foot on the clutch. The vibration changed!!! I bounced a couple of more times and it totally disappeared!!!! I didn't need to touch the clutch again for the last hour and a half home. I can't tell you what a relief it was to not only have the vibration disappear but to finally know that I had control of it. Even Pepe, who hadn't laid his head down the whole trip because of vibration, laid it down and slept!

I know I've got to fix the vibration in both the engine and the drive line some day; but, until I do, I at least have a temporary solution that works like a charm.