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ricosan

Drive line vibration

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Good Morning Folks,

I have a 1932 Marmon that has a severe driveline vibration. It starts at about 25mph and continues to worsen until it becomes intolerable above 50mph. I can push in the clutch at this point and allow the engine to drop to idle speed and yet the vibration persists, lessening as the car slows. I've had the drive shaft removed, greased and the U-joints inspected. We had the drive shaft professionally balanced but the vibration still persists.

We also removed the transmission and took it completely apart, cleaned and inspected all gears and bearings and then reassembled it.

We checked the drive shaft for run-out while it was mounted in the car. An insignificant amount of run-out was found.

We balance the wheels.

My mechanic says it's not the u-joints as this would have shown up during the balancing and I respect his knowledge and experience very much but I just don't know where else to go with this. Has anyone had experience with this aggravation. I there somewhere else to look?

ricosan

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Have you checked for bent wheels or out of round tires? I see you have 2 spares, try putting the spares on the front, if nothing changes replace the back tires with the ones you took off the front.

Wheels can be straight and properly balanced and still have a vibration if the tires are out of round. Yours seems to be a severe case, the only time I had a vibration that bad, I left a tire iron inside the tire.

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Hey Rusty,

I thought it may be the wheels or tires too so I found a place that could balance "buffalo wheels". They checked for run out. Wheels were good. Two of the tires had run out (front left and rear right) but not severe. I'm going to replace them but I don't think that the wheels and tires are the source of the vibration. I don't get any vibration through the steering wheel. This is more of a staccato vibration and it starts at low speeds.

ricosan

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What do you mean as the run out is not severe? If the run out is more than about .040", you can get a good vibration.

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There are machines to grind down out of round tires and make them balance. The better equipped tire stores have them. Might be better and cheaper than new tires. I have heard that a lot of vintage size tires are lumpy and out of round, and need grinding to true them up.

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I know that my local Chevrolet dealer has one of those machines. It will tell the stiffness of the tire as it is rolling.

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Did you try putting jackstands under the frame with the rear wheels off the ground and running at different speeds? This would eliminate the front wheels and suspension. You also could put a jack under the rear axle to vary the suspension height or take off the rear wheels to see if it makes a difference.

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Are the U-joints out of time? If there is an expansion joint in the driveshaft between the U-joints then the timing of the 2 relative to each other could have been upset by incorrect assembly.

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I had to look the car up to see some build specs on it to make a opinion . I seen that it has front and rear leaf spring suspension . Even today cars and pick ups are having problems with the bushings/collars getting worn threw . Maybe inspect all 4 corners of leaf spring hinge points along with if the springs are wrapped in rubber where they mount to the axle . Just offering up options . Good luck and a fine piece of artwork .

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Are the U-joints out of time? If there is an expansion joint in the driveshaft between the U-joints then the timing of the 2 relative to each other could have been upset by incorrect assembly.

I agree with Layden. In Auburns the U-joints are timed at 90 degrees.

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Good Morning Folks,

Larry, I'm not sure exactly what kind of machine it was. It measured separately both wheel run-out as well as tire run-out and did the balancing too. I do need to replace two of the tires with run-out of approximately 1/4". However I just don't feel that the problem is in the tires because of the type of vibration I feel. If it were tires (18") I would more likely feel a rhythmic bumping increasing with speed. The vibration I'm feeling is a very rapid stacatto beat that becomes more insistent as speed is increased.

Mister, I haven't tried that yet but it sounds like it may give up some valuable information about what's going on with the DS. I'll suggest it when I'm back to the shop and have access to a lift.

Buick, good idea. I haven't paid much attention to the shackles. They all have grease fitings. It wouldn't hurt to hit them all with a fresh bit of grease.

Layden & Curti, we were very careful to make sure that the drive shaft was put back together "in phase" is what he called it. The last time I had it in he suggested that we take it loose and reinstall slightly "out of phase" to see if that had any effect. Unfortunately we didn't get to it. That's something that we will definitely do when I tske the car in next week. Right now I'm ready to try anything.

I would like to replace the u-joints but I've been unable to find anyone who could cross reference the Spicer u-joint original part number SP- 3 1/2-64.

ricosan

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Run it with the back end elevated with the wheels on and off. You could also put the front wheels on and run them up. Make sure you have good ventilation when you do this!

I understand some old wheels did not necessarily have the stud holes concentric with the centre hole of the wheel. If this is true, balancing an old wheel must be done with it mounted on the studs, not on a central cone mandrel.

Grease won't fix worn-out shackles - it will just come out the ends. Get in there with a pry bar and wiggle it about to check for movement in the shackles.

Have you checked (camber and) caster on the front wheels? You may get a shimmy if the caster is not right (not negative enough?). You haven't said anything about a vibration in the steering wheel so this is probably not "it".

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Did this condition appear all at once or was it gradually growing in severity over time? If possible, you may want to swap all four wheels/tires with a known good set if you can find someone willing to lend you theirs for test purposes. Another strong possible cause could be collapsed, oil soaked motor/transmission mounts. Keep us informed of your progress. Good luck!

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Pinion bearing ! ! ! Check your pinion bearing/bearings......... regards; Jerry Janson

A good indicator of this could be signs of heavy oil seepage around the pinion seal. Unless, of course, the differential is bone dry.

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Good morning Guys,

Spinneyhill - I'm going to try that today if I can find someone to help me. I'll try it with the tires on and off the car to see if I can feel/see the vibration. I'll let you know what i find.

Larryschramm - Thanks for the video. That's what we used to check for run-out on the drive shaft. Although I watched it performed, I don't recall the exact figures but my mechanic declared it "good".

Larry w - No this condition came with the delivery of the car last year. I think that the transmission is mounted solid to the frame without any bushings.

Oldiron - We removed the differential cover and inspected the ring and pinion. I had on hand new replacement ring and pinion bearings but upon inspection, he said it didn't need it.

ricosan

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Does the sound/vibration change when the car is under acceleration versus under deceleration? If there is a crack in the ring gear it will make a similar, but not same noise under acceleration/deceleration.

If I remember correctly, a year or so ago, you had a thread going about the same car, same vibration.

At that time, there was some discussion about your transmission, having either an Overdrive on the rear of the trans. or a Freewheeling system on the trans. It was determined, I think, that it is a freewheeling system

Freewheeling can 'chatter' or slip/grab/slip/grab. The parts in the freewheeling system can be potmetal or brass.

I'd try locking out the freewheeling and see if there is any change. Then try running up to the start of the noise/vibration in 2nd gear. and see if it is still there or has changed.

Can you feel the vibration/noise through the gearshift lever? or is is more pronounced in the back seat?

GLong

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Could the drive shaft be bent? It would not show if you measured runout at the universals.

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Greg - It's the same under acceleration and deceleration. When I push the clutch in at 50mph and let the engine idle, the vibration is very noticeable.

Yea Greg, this is the same problem I've been chasing since I got the car to go faster than 30mph. This vibration really sucks the pleasure out of the driving experience. During the past year I've gone through the whole drive system from the rear axle bearings, differential, drive shaft and we took the transmission completely apart and cleaned and examined every bearing and gear. Everything looked good. It turns out it has the freewheeling attachment at the rear of the transmission, no overdrive like the seller said. I don't drive with "freewheeling" engaged. The transmission appears to be solid.

I can feel a bit of vibration through the gear shift lever but mostly from the floor boards as well as from the seat.

Spinney - I don't recall that he measured runout in the middle of the shaft. I'll ask him about that. I thought about that very thing since I've had the car back this past week. Could it be a bent shaft? I assumed that the straightness of the shaft would be measured during or before the balance process. I'll let you know what he says.

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Are you sure that the transmission and differential have the correct lubricant? Perhaps that 600W that I've seen mentioned elsewhere is what's required.

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I suppose if the shaft was balanced, it should not be bent. If it is not in the steering wheel it might not be in the front wheels. If it is not very noticeable in the gear lever, it is unlikely to be close to the gear box. If it is through the seat and floor, it sounds like wheels and suspension. Worn shackles will make the car handle poorly - mine hopped about and over-steered suddenly while in a corner, a bit like it had soft rear tires.

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Hey Guys,

Larry - We put 140 WT oil in the transmission. I like your idea, maybe a higher viscosity oil would make it quieter too.

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Spinney - Thanks for the heads up. I haven't noticed any squirrely road manners but I will check the shackles next week when I get it back on the lift. I'm all for making the driving experience as pleasant as possible.

ricosan

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Crawl under the car when it is on the ground, weight on the wheels. Look at the angle the pinion shaft in the differential and the centerline of the driveshaft make. If the pinion shaft is not within say 5*-10* of the centerline of the driveshaft, then the vibration could be too much angle for the universal joints to work around.

You can shim the rear differential housing where it is clamped to the rear springs. There are wedge shaped shims used for changing the caster angle of the front axle, and the same shims can be used on the rear axle to reduce the U-Joint angle.

I too don't think any driveshaft shop could spin and balance a driveshaft without noticing if it had a significant bow or bend in it..

Your description of the vibration being there with the clutch in, the engine at idle, and not feeling it in the gearshift, but the vibration seems to come from under the rear floorboards. And, since you have inspected and or replaced wheel bearings, differential bearings, etc.. So the only item to truly vibrate would be the driveshaft.

You can do your own driveshaft run-out test just by clamping a yardstick to the frame with the end near the center of the driveshaft, slowly turn the driveshaft and look for the gap between the stick and the shaft to change. If there is a noticable change in the gap, then the driveshaft WILL VIBRATE.

A driveshaft can be balanced at a given speed, even if bent. Then IF the shaft is bent, it will bend more with higher rpm. and will then be out of balance at the higher rpm.

So, check the U-joint angle, and check the runout of the driveshaft at the center of the shaft..

Good Luck. Let us know what you find.

GLong

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