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Drive line vibration


ricosan

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Hi Ricosan,

I work with turbo rotating machinery that spins at very high rpms, and the vibration sensors that OldIron mentions above may not be suitable as most vibration monitors measure in extremely small measurements such as velocity, frequency or displacements in micrometers . These systems are used to detect levels of vibration that are not detectable by the human senses. From your description the vibration issue you are experiencing is at a level way higher than Condition Based Vibration Monitoring Equipment that is used on Turbo machinery such as Bentley Nevada systems etc.

Given you have had the driveshaft dynamically balanced, its still only a single component in the string of the drive line. It doesent take into account the other components that are rotating at the same time at different rpms hence different frequencies..... Once you have run the vehicle with the wheels off and if the vibe still exits, maybe try attaching weights to the driveshaft using hose clamps ( bearing in mind they will have rotating mass themselves. ) A visual check under the vehicle when its vibrating at the levels you describe may well identify the root cause area...... then suggest to try the temporary weight attachments on the rotating elements or driveshaft. In the middle of the shaft may be a good place to start as its the longest area of unsupported mass, and most susceptible to whip of dynamic unbalance as the rpms increase. I had good success with this method in other applications on low to medium speed applications... Its worth a try as you have nothing to lose but lots to gain :)

Look forward to see the results and hope it goes someways to help identify the problem area that's the root casue of the vibration, for like any vibrations, the lower the better as it can cause massive amounts of undue wear over time.

Good luck :)

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Another off-the-wall thought - I am working on the lathe at the moment. If you can beg or borrow a dial indicator with a magnetic base, you can look for run-out on the drive shaft, pinion (bearing) in the diff., rear pinion bearing in the gear box etc.. If something is running off-centre, it will vibrate. If you look underneath while running the driven wheels, you might even see the lateral movement in a rotating part. Make sure the car is on secure stands of some sort while running it, not just a jack (or even two jacks).

Are there any collapsed bearing noises - such as a rumble - from the gearbox back?

Another thought: Studebakers must have the gearbox accurately centred on the crankshaft ("dial indicated"). Does the Marmon require this? Could misalignment cause vibration? It will certainly damage the pinion bearings and gear.

The wheels and tires have been balanced. Are all the weights still on? Are they all together on a wheel - if there is separation between weights on the same side of the rim, it is a dud balancing job, or some are missing.

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I think the right thing to do is put the car on jack stands. I remember in the first thread on this problem in this car, you had the car up and ran it, listening for noises and the vibration.

It is probable that the u-joint flanges have a matching raised surface on one mating surface/flange and a matching recessed spot on the other flange. If the two don't fit tightly, the bolts holding the flanges together are not able to center the two flanges.

Since your vibration starts at roughly the same speed, and doesn't change with acceleration or deceleration, it has to be something like the driveshaft bent, bowed, or the flanges not mating concentrically.

One other thought: The buffalo wire wheels, the way they mount to their matching hubs is a bit 'odd'. Is there any chance that one of the wheels is not the exact same hub as the rest of the wheels? Or are the two rear wheel/knockoff hubs the same on both sides. ? Do a few comparrison measurements.

A loose wheel could make a noise in the speed ranges and circumstances you describe. If it is a wheel, it would go away almost 100% if the car's weight was not on the wheel. So it should be noticably different if the car is run on jack stands.

I think in the last thread, when you had the car up and running, you listened to each axle near the spring, and thought you found a bad bearing or two. since you have now looked at all of those items, maybe you have a worn buffalo wire wheel hub, or a worn axle hub. And the 'rattle-room' is what is making the noise and vibrations..

Can you easlily swap the front tire/wheels for the rears??

Oh, take a close look at the wires in the wheels, and the hub and rim where the wires go through.. are there any rust stains? like rust is 'leaking' out from around a spoke or two? Any cracks in the hub or wheel rim? The flexing of a wire wheel that has cracks, or loose wire spokes could also make your noise and vibration.

More ideas rattling around in my head, I thought I'd put them down, someone, sometime will find the big 'AH Hah' !! and I can't wait to hear what it is.

GLong

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Hey Guys,

I've had the car at the shop for the past week. My mechanic was able to get the Schebler carburetor tuned so that the engine doesn't stop running everytime I come to a stop. We also installed an in-line gascock so that I can run the gas out of the carburetor when I park in the garage. Scheblers tend to leak when the engine is shut down.

I talked with my mechanic again about the vibration. I insisted that he take a ride with me to a part of the highway that had a big hill as I was sure he would be convinced as i am that the vibration in in the drive line. He wasn't convinced. He believes that the vibration is in the tires. I believe it's in the drive line but I will be happy if we find it in the tires.

We took one of the side-mounted tires from the car and took it to the local Firestone dealer who had machine for truing tires. These machines were popular back in the days before radial tires and most large tire stores had one. The machine was way in the back and covered with dust. No one new exactly how to use it but my mechanic found a manual on the internet. We plan to experiment on this tire and if it works, we'll true the other two tires that are mounted on the car and are out of round.

ricosan

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  • 2 weeks later...

Hey Guys,

Yesterday I got the tires trued (shaved the rubber until the tire was true) and balanced. I reinstalled them on the car this morning. I took it for a ride on the open highway. It feels better but not noticeably so. I now don't feel any vibration through the steering wheel or the seat but the vibration I'm concerned about is still there. I can push the clutch in at 55 mph and let the engine go to idle. I get a vibration that is fast (staccato) and intense then gradually lessens in intensity as the car begins to slow.

My mechanic has agreed to make up a new drive shaft with modern u-joints that have grease fittings. I will keep the old drive shaft for the next owner. They can simply bolt it back in if they are more interested in originality than driveabelity. I want to drive the car and I'm very concerned that serious damage may occur if I don't fix the vibration.

If this doesn't do it, we move into the engine.

ricosan

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Good Morning,

I was able to squeeze under the car(barely) using my creeper. There was not a good spot to place the protractor so i had to take a couple of bolts loose. These are numbers I came up with. My math works out to 4 degrees off. Is this a significant amount?

287180d1419002378-drive-line-vibration-driveline-angles-copy.jpg

Is 4 degrees significant? YES. You have discovered the problem! 4 degree difference (unless corrected some other way) will produce vibration. Faster you go----faster (and more violent) the vibration.

This video shows a guy with a 4 degree difference. He explains why this causes vibration and how he fixed it. He uses the steel angle shims between the axle mounts and the springs that Jack M wrote about three weeks ago.

This is not some big mystery. It is easy to solve. Find a mechanic that has had experience with this (like one that builds hot rods). He will fix this for you!

10 new driveshafts will not fix this vibration and it is not in the engine as Spinneyhill pointed out. I am sure your mechanic is excellent, but he is apparently not able to fix this problem. This is not something in which he has significant experience.

Edited by Dwight Romberger (see edit history)
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Yes. In other words the centerlines must be parallel.

How much "out of phase is too much?" The best I can gather from the literature is that some literature says there must be zero degree. Others say 1 degree is acceptable if the 1 degree is the pinion angle tilted down1 degree in relation to the transmission angle.

Edited by Dwight Romberger (see edit history)
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  • 2 weeks later...

Hey Guys,

Well today was the big day. We installed a 2 1/2 degree shim at the springs. This unfortunately made the vibration worse! I can't understand it. I'll recheck the drive angles when we have the old drive shaft completely out to see if I measured wrong.

I talked with my mechanic about making up a new drive shaft with modern universal joints. This hopefully will once and for all eliminate the drive shaft as the culprit in this vibration saga.

If the new DS doesn't do it, we move into the pressure plate clutch area.

ricosan

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Um, it seems clear to me that if the shim made it worse, there is nothing wrong with the drive train, including drive shaft and gearbox and clutch. You proved the clutch was not involved by coasting in neutral while moving and it made no difference. Try the shim on the other side, tilting the diff. the other way.

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Hey Dwight,

Since shims are relatively inexpensive, My mechanic suggested I get both a 4 degree shim and a 2 1/2 degree shim. We decided to go with the 2 1/2 first and see how the vibration "responded" to that. Since it made the vibration worse, we felt trying the 4 degree would make it worse.

I am completely baffled as to why it got worse. I keep going over how we measured the angle and how we installed the shims. (my mechanic measured the angle too. We installed the shims with the thick part of the shim facing the front of the car. This pushed the differential up bringing it closer to parallel with the transmission.

Several of you have suggested I reverse the shim. I'm willing to try it but why do you think this might work? It does sound logical but it kinda stands the "science" on its head but it does make sense in an odd way. When I take my car in next week to measure for the drive shaft, I'll talk to my mechanic about reversing the shims.

Tomorrow, I'm going to put the car back on jack stands and take angle measurements again just to recheck to make sure I haven't erred in some way. It's not very easy to read the dial on the protractor.

ricosan:confused:

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I suggest you take the angle measurements with the car resting as normal with all its weight on ALL FOUR WHEELS, such as on a ramp-type hoist. It seems to me that when the car is on jack stands, the rear axle will not be in its normal position--that is, the axle assembly will be either hanging on the springs if the stands are under the frame, or some of the spring action is taken up if the stands are under the axle housing. Either way, on jack stands you will probably not be getting the same angle measurements as if the car is resting on all four wheels.

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  • 5 weeks later...

Hey Guys,

We put the new drive shaft in Yesterday. Good news and bad news. The car rolls much easier and when I push the clutch in at speed, the stacatto vibration that I felt previously isn't there but unfortunately much of the vibration is still in the system.

The old drive shaft threw lubrication out at both U joints (pic). This new shaft has grease fittings so no more mess under the car.

I am going to box up the old drive shaft for sale with the car when the time comes. We made no modifications to the drive line itself so the old drive shaft will bolt back in easily.

From here we keep on working. I don't think that the problem is in the transmission. I think it may be in the flywheel/pressure plate area.

I was really hoping that this would solve the mystery of the vibration. I can't say I'm not disappointed but this new drive shaft took me just a little closer to the prize. It's one more thing that can now be ruled out.

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"We installed the shims with the thick part of the shim facing the front of the car. This pushed the differential up bringing it closer to parallel with the transmission."

That may be the problem. If the drive shaft is in a straight line with the trans and/or diff it will vibrate. The driveshaft must be at an angle, in other words the universal joints must work as the shaft rotates and they must both be at the same angle.

http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

Edited by Rusty_OToole (see edit history)
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When you push in the clutch at speed, if it is the clutch/flywheel, the vibration will vary with engine speed. From all the several pages of descriptions of the vibration, the vibration is created by something AFTER the clutch flywheel, and is dependent on road speed, not engine RPM.

I suggest that the vibration and 'staccato' noise are in the transmission or the freewheeling unit. There can be bearings that are very bad, or gear teeth missing, or freewheeling 'one way' rollers that are flat-sided, or several other possible causes of vibration in the transmission.

Did you start and run the engine with the trans either in or out of gear when the driveshaft was removed?

GLong

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Good Morning Guys,

I disconnected the drive shaft from the transmission this morning, started the engine and brought up the temperature. I brought the engine RPMs up and as I did I found a distinctly familiar vibration. I then engaged the transmission in first gear and then moved on up to 2nd and 3rd. Again as the speedometer rose I found all the same vibrations but the vibrations didn't increase when the transmission was engaged so I think that the vibration is forward of the transmission. It may be in the pressure plate or the clutch plate. It could be in the engine i suppose?

I have a Marmon get together in May that I want to travel to. I hope I can get this vibration out before then.

Thanks guys for the great suggestions. I'm beating myself up for not thinking of it before!

ricosan

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First Born - The engine runs pretty good. In the past 12 months I've replaced all of the spark plug wires, new points and condenser, new spark plugs and new coil. Also had the carburetor professionally rebuilt. Compression is good. 7 cylinders 64 lbs and 1 at 70 lbs. I believe it is still using the babbit type bearings but I haven't opened up the engine to see.

Spinney - I take the car in next week to replace the leaky cork seals on the side valve cover. This will entail removing all the manifolds and most everything else on that side of the engine in order to expose the valve stems. We plan to adjust all of the valves when we have every thing off. I don't want to have to do it again.

I'm not certain but I don't think this car has a damper or not one that I recognize anyhow.

ricosan

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I don't know what's causing your vibration. But I noticed your compression readings, and they seem low. Your engine probably had a 5.5 to 1 compression ratio originally, and multiplying that times 14.7 psi (atmospheric pressure) yields 80 psi. Did you check the compression with the engine fully warmed up, all spark plugs out and a fully charged battery? I am not saying that compression is the cause of your vibration. But it's possible that the engine needs closer attention to assess its condition.

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Have you (or your mechanic) given any thought to the engine mountings or exhaust/muffler causing the vibrations. Don't know anything about the Marmon engine mounts but the photo of the rear engine mount in post 59 appears to rubber insulated on the cross bar. Perhaps this needs replacing. Hope you find the cause as there is nothing more frustrating than trying to solve these issues.

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Good Morning Stude,

I think that what you see in post #59 is the support for the tail of the transmission. This is my first antique car so I am still learning every day. I've looked for "motor mounts" as I'm accustomed to seeing on most all the cars I've owned but this car looks to me as if this engine is bolted solid to the frame.

ricosan

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Good Morning Stude,

I think that what you see in post #59 is the support for the tail of the transmission. This is my first antique car so I am still learning every day. I've looked for "motor mounts" as I'm accustomed to seeing on most all the cars I've owned but this car looks to me as if this engine is bolted solid to the frame.

ricosan

The first car to use "modern" rubber motor mounts was the four cylinder 1932 Plymouth. Prior to that all cars had their engines bolted directly to the frame. Cars with more than four cylinders were not subject to as much vibration but by about 1935 virtually all auto makers were using them.

Terry

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The first car to use "modern" rubber motor mounts was the four cylinder 1932 Plymouth. Prior to that all cars had their engines bolted directly to the frame. Cars with more than four cylinders were not subject to as much vibration but by about 1935 virtually all auto makers were using them.

Terry

Not true. My 1931 Dodge Brothers had rubber insulators (motor mounts). A few earlier Chrysler products had them.

Edited by keiser31 (see edit history)
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Hi ricosan, I would look to see if there is an inspection plate on the top of the bellhousing. If so, remove it and look the clutch pressure plate 'cover' and arms etc to see if there is anything not symetrical, like different size bolts or washers on the clutch, bent arms, missing springs etc. Anything that would change the rotating balance of the clutch assembly.

I'd also be concerned about and want to check to see if the flywheel is loose. This could be a big problem is the bolts have wollowed out the holes in the crank and or flywheel. If you can, put a pry bar on the outer edge of the flywheel, and gently pry/push it fore and aft. there will be a few thousandths of crankshaft endplay, but not a significant amount. usually about .003"-.008" for a big inline engine.

Your pilot bearing in the end of the crankshaft, that centers and supports the end of the trans' input shaft could be really bad, and allow the input to be off-center when the clutch is trapped between the pressure plate and flywheel. Usually if the pilot bearing is bad, the clutch will chatter badly when the clutch is engaging.

In your original description of the vibration and noises, it was reported that when you pushed in the clutch at speed, the vibration continued unchanged. I believe you have more than one source for vibration: the new driveshaft seems to have eliminated some of the problems, but not all.

Looking forward to the next bit of info.

GLong

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Guest kaycee

The factory brochure says the engine has a balancer on it. They call it a High frequency- oscillating vibration dampener in the

sales manual.

The "balancer" could also cause a vibration in the drive train.

kaycee

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