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ricosan

Drive line vibration

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Does the driveshaft have to be 'wedged' into it's position between the rear output shaft of the trans and the input flange of the differential? Or, is it stretched when the U-joint flange bolts are tightened?

If the slip joint in the driveshaft is either compressed tight, or stretched too far, the shaft will vibrate. Most of the slip joints have a grease fitting. Often the spline is over greased and the grease acts like a hydraulic pump and pushes the splined shaft back, making the driveshaft have a lot of pressure on the U-joints.

Something else to check..

Greg L

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I think GLONG is on to the source of your problem. The driveshaft is vibrating because the angle of the transmission output shaft and the pinion angle is too far off. The faster it turns, the worse if would vibrate. The angle should be the same or the pinion angle pointed down about 2-3 degrees. The hot rod guys know all about this. A picture is worth a thousand words:

post-63449-143142888155_thumb.jpg

post-63449-143142888152_thumb.jpg

This describes it better than I can: http://jniolon.clubfte.com/drivelinephasing/drivelinephasing.html

Edited by Dwight Romberger (see edit history)

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I think GLONG is on to the source of your problem. The driveshaft is vibrating because the angle of the transmission output shaft and the pinion angle is too far off. The faster it turns, the worse if would vibrate. The angle should be the same or the pinion angle pointed down about 2-3 degrees. The hot rod guys know all about this. A picture is worth a thousand words:

[ATTACH=CONFIG]286730[/ATTACH]

[ATTACH=CONFIG]286729[/ATTACH]

This describes it better than I can: http://jniolon.clubfte.com/drivelinephasing/drivelinephasing.html

There are other things which can affect driveshaft angle. Has the car ever had accident damage? Is the rear axle actually at a right angle to the driveshaft or is one side farther forward?rearward than the other? Is the engine/transmission in line with the driveshaft side to side? After 80+ years the rear springs have probably flattened out which will change the angle.

Terry

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[TABLE]

<tbody>[TR]

[TD=width: 100%]

post-63449-143142888722_thumb.jpg

[/TD]

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</tbody>[/TABLE]

Drawing A represents the wrong way to offset an engine. Done this way you are sure to have driveshaft vibration, noise and U-joint wear.

Drawing B shows the correct method of offsetting the engine.

It doesn't matter that the two U-joints are not on the same centerline from the front of the frame to the back (my engine is set right 2" and the pinion is 1-1/2" right.) It only matters that their individual centerlines are parallel..

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[TABLE]

<tbody>[TR]

[TD]

[ATTACH=CONFIG]286772[/ATTACH]

[/TD]

[/TR]

</tbody>[/TABLE]

Drawing A represents the wrong way to offset an engine. Done this way you are sure to have driveshaft vibration, noise and U-joint wear.

Drawing B shows the correct method of offsetting the engine.

It doesn't matter that the two U-joints are not on the same centerline from the front of the frame to the back (my engine is set right 2" and the pinion is 1-1/2" right.) It only matters that their individual centerlines are parallel..

Drawing A is what I was referring to in post 29. As long as the centrelines of the engine and rear axle are parallel to each other as in drawing B, they can be offset. Most cars with engines mounted north/south have their engines offset to the right to compensate for the driver's weight.

Terry

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Not only side to side but up and down as well.

As stated parallel centerlines. You can usually put an angle gauge on the engine somewhere that is straight with the oil pan and find a place on the rear end that is square to the pinion shaft and align accordingly.

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Wow! This is great information! I don't recall if these offset measurements were ever taken when we were working with the drive shaft. I'm going to buy an angle indicator today. These are measurements that I can take to my mechanic. I'm excited. I hope this solves the mystery as I felt that we had exhausted every remedy and had reached a dead end. Its an 82 year old car and the springs may not be what they used to be. If all goes well I will be able to measure angles this afternoon.

ricosan

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I am not familiar with the older u-joint set ups, but what you have could be more sensitive to off angled alignment than more modern u-joints.

I know I have had several cars that sagged from age but I have never experienced the problems that you describe to the extent that it couldn't be driven.

The gauge that I use when building a car is a simple gravity deal with a magnet on the bottom that I got from Harbor Freight or the likes.

Recently I was setting up a chassis and the thing was acting up. I took it apart and it is plastic where the indicator hangs and that was dry and sticking a bit. I little graphite lube fixed that.

In this picture the camera is at an angle so it doesn't look right. But the rear end is square and the engine is square, so side to side I am good. When I get the weight of the body and such I may have to use angled shims between the axle mounts and springs for the up and down to be correct.

As stated earlier, sometimes a slight down angle on the rear end is acceptable, especially if doing a lot of hard accelerating.

post-52542-143142891239_thumb.jpg

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I like Dwight's video. But that guy is working in a drive shaft that I call a two piece shaft, I suspect that it has a bearing in the middle.

And his tools are a BUNCH better than what I use.

I am just an old rodder that makes do I guess.

Hope you find your vibration regardless.

Fun stuff, especially when you finally figure it out.

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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?

post-97329-143142893642_thumb.jpg

Edited by ricosan (see edit history)

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ricosan; if I'm reading the comments correctly, you still have not found your problem. There is one sure way perhaps, and that would be with a vibration meter. A vibration meter normally reads the harmonic output from an attached sensor; i.e. the sensor being fixed,(strapped), to a bearing housing so that it may read the harmonic frequency of that bearing when it is in motion. (A deteriorating bearing or bent or otherwise misaligned shaft, putting uneven loads on the bearing would allow for a higher harmonic frequency reading than normal, thus indicating the problem area.). This could be done at all bearing points to determine the source of your vibration, One such manufacturer of a portable vibration meter that is also reasonably priced and should lend itself to aiding you in this endeavor is Balmac, of Plain City, Ohio. ( balmacinc.com or tel 614-873-8222) again, good luck; Jerry Janson

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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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Has anyone checked for a bent rear axle ?

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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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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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When you push the clutch and the engine goes to idle and the vibration is still there, it means the engine is not the problem. You could push in the clutch at 55 m.p.h. and stop the engine to prove it.

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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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The trans output "down" angle must equal the differential "up" angle. ie: if trans is 2* down then the differential should be 2* up.

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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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