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.

[flatjack9]

Seems like you have an out of balance situation in the engine and also in the flywheel/clutch assembly. Was the engine balanced when you had it built? I would guess no.

[rotorwrench]

You may have something going on with the clutch disk or the input shaft on the transmission. It could be the pilot bearing too. If the clutch disk gets off center due to some loosesness in the shaft, it may cause a vibration. Throw out bearings usually just make noise when they are going south since the outer diameter is smaller and closer to the center of the shaft. The only other thing I can think of would be a problem with the clutch cover pressure ring moving around too much due to wear.

[Bolts]

Professor, is the clutch behaving nicely and working as it should? Does it chatter when you engage it and/or is it adjusted to it's extremes in order to release?
Also, have you checked the rear trans mount for loose bolts or bad rubber?
Are the motor mounts loose or a donut bad? I assume the trans is bolted tight.
Is there noise that accompanies the vibration, like whining or rubbing sounds?
Finally, is the rear end bolted down tight and is the radius rod attachment at the Y good?
I am inclined to agree with rotorwrench about the looseness of the trans pilot shaft, letting the disc wobble a little bit to get off center, but I would think you would hear something.

[Kahuna]

Old Henry
It is possible that there is only 1 problem. My guess is the clutch/transmission

[Bill OH]

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I had the same problem with a 47 Ford 2 ton truck - vibration and it would disappear if I slipped the clutch to the right position in relation to the flywheel. Truck had been lengthened and the midship bearing not moved - drive shaft to long even though it had been balanced. I would take a look at the midship bearing in the torque tube.

[Bassman/NZ]

So ya got the gravel rash on yer back for nothing?

[Old Henry]

Originally Posted by flatjack9

Seems like you have an out of balance situation in the engine and also in the flywheel/clutch assembly. Was the engine balanced when you had it built? I would guess no.

Don't know of any balancing done on the engine when it was rebuilt in June since it wasn't started until I took it and installed it but I didn't notice the current vibration until about December.

Originally Posted by Bolts

Professor, is the clutch behaving nicely and working as it should? Does it chatter when you engage it and/or is it adjusted to it's extremes in order to release?
Also, have you checked the rear trans mount for loose bolts or bad rubber?
Are the motor mounts loose or a donut bad? I assume the trans is bolted tight.
Is there noise that accompanies the vibration, like whining or rubbing sounds?
Finally, is the rear end bolted down tight and is the radius rod attachment at the Y good?
I am inclined to agree with rotorwrench about the looseness of the trans pilot shaft, letting the disc wobble a little bit to get off center, but I would think you would hear something.

The clutch has chattered since the engine was rebuilt, the flywheel turned and the clutch pressure plate replace in June. Other than that it seems to work fine.

Motor mounts are new and I just checked the trans mounts and they weren't worn or loose.

No noise, whining, nor rubbing sounds.

Originally Posted by Bill OH

I had the same problem with a 47 Ford 2 ton truck - vibration and it would disappear if I slipped the clutch to the right position in relation to the flywheel. Truck had been lengthened and the midship bearing not moved - drive shaft to long even though it had been balanced. I would take a look at the midship bearing in the torque tube.

I will start my repairs rebuilding the torque tube with new U-joint, front and mid bearing.

[jimTN]

Vibration is dangerous, will sooner or later shake something loose!

[1931 flamingo]

Was it you or someone else that had engine work done a while ago??
Paul in CT

[Old Henry]

Originally Posted by 1931 flamingo

Was it you or someone else that had engine work done a while ago??
Paul in CT

I doubt I'm the only one that's had engine work done but my engine was rebuilt in June when a piston came apart.

[Bolts]

Originally Posted by Bill OH

I had the same problem with a 47 Ford 2 ton truck - vibration and it would disappear if I slipped the clutch to the right position in relation to the flywheel. Truck had been lengthened and the midship bearing not moved - drive shaft to long even though it had been balanced. I would take a look at the midship bearing in the torque tube.

Trying to learn here.
I was thinking about the center bearing causing the vibration and how clutching could stop it. From reading previous posts, the bearing was added to prevent vibration, so a defective bearing causing the vibration makes sense.

But, what does the clutch have to do with it?

Clutching releases the driveshaft from the engine, but the driveshaft continues to spin, now driven by the wheels instead of the engine. Like letting off the gas and coasting, sort of.

So, could it be that the torque on the drive shaft causes the bad bearing to twist slightly and bind. Clutching temporarily releases the pressure on the bearing because the shaft torsion decreases and the bearing can relax and realign itself on the drive shaft. Then, the clutch is let out and the aligned bearing spins easier until it eventually gets out of alignment from heat or vibration and again twists a little bit so that it forces the shaft to run out slightly and vibration starts again?

Comments?

[Marv]

Whatever is causing the vibration, it can not be good running it that way. Something is going to come apart sooner or later. I would be making my trips short and close to home if i was going to run her till she comes apart.

[Teich]

Look at the clutch/disc/pilot bearing. This quick release of clutch is likely causing the disc to reposition to the good spot, should not change anything with the center bearing. 24" wheels will prevent the road rash. Laurie

[Old Henry]

I don't really enjoy working on my car but I absolutely love driving it. Since I have not found anyone handy to fix it when it needs fixed so that I can just drive it I've got to do it. And, I have more money than time so, in most cases, rather than try to fix something I'd just as soon replace it.

So, now I'm ready to get rid of the vibration in my drive line by taking everything apart between the differential and the engine crank shaft and replace anything and everything that might be worn out and causing my vibration since I don't have a lot of confidence in being able to diagnose what the cause of the vibration is.

So far, in posts on this thread, I think the following parts have been suspected to cause the vibration and might as well be replaced:

Drive shaft center bearing, part # 78-4658
U-joint , part # B-7090
Clutch release bearing, part # 78-7580A
Transmission input shaft. Is that part # 81A-7017?
Pilot bearing, part # B-7025-A
Clutch cover pressure ring. Is that part # 19A-7563-A?
Clutch disc. Is that part # 51A-7550-A?

No one mentioned the front drive shaft bearing, Part # B-4645-A. What about that?











Are there any other parts that anyone would suggest replacing that might be causing the vibration?

Also, while I've got it apart I'd like to get rid of my clutch chatter/shudder. Any other parts to replace to get rid of that?

[ford38v8]

Henry, diagnosis without benefit of inspection is flying blind. Before you go buying parts you may not need, carefully dismantle and inspect as you go. Chances are that you may only have a loose bolt or two on your clutch housing. These are the things you find out only when you have your eyes open as you dismantle.

[Old Henry]

Originally Posted by ford38v8

Henry, diagnosis without benefit of inspection is flying blind. Before you go buying parts you may not need, carefully dismantle and inspect as you go. Chances are that you may only have a loose bolt or two on your clutch housing. These are the things you find out only when you have your eyes open as you dismantle.

Unfortunately, I had a bad experience with that approach with a noise that I thought was near my differential and took the torque tube off to find my sleeve pins all busted out and ground up by the pinion nut and lock washers and thought that was the cause of my noise so fixed those and put it all back together and still had the noise that I then concluded had to be inside of the differential which I didn't want to tackle so ended up replacing the whole rear axle, differential, and torque tube as a unit which I would have been better off doing in the first place. https://www.fordbarn.com/forum/showthread.php?t=89703

[Lawrie]

Henry, I feel for you,like you I do lots of miles in my 33,
It had a vibe somewhere in the driveline,
The previous owner even changed the rear end.
This is a list of things I tried,new old stock universal,new gearbox bearings and mount,new clutch ,all new bearings in the rear end and driveshaft,,over a period of some 4 years I tried every thing,once on a trip it went 1600 miles over 3 days as smooth as ,then as I got off the gas to exit the freeway,away it went, I thought it was the u/joint running dry so I even made and fitted a little tank on the firewall connected to the u/joint by a small hose so I could dump some gear oil in on the run.
Finally I got the sh--ts.
I took the rear out,gearbox out, fitted a new dick spader driveshft,3.78 ring and pinion, new old stock ford u/joint,this I made a mandril and got the machine shop to balance as well as the driveshaft. checked the front driveshaft bearing,it had .016 up and down play,sorted through my nos bearings and sleeves and got it down to .005.
reassembled at the stuff back .AND its been good for about 4 years and probably 15-20000 miles.
I dare not say too much incase it comes back.
Lawrie

[JWL]

I have another vote for pilot bearing missing or worn or pilot shank on trans. input shaft worn. Neither are fun to fix.

[big job]

I had the same symtom. Finding putting the clutch down the mainshaft
centered itself- solution wiped out pilot bushing / replaced with a ball
bearing pilot vibration gone.....