Machine Gun

1964 Skylark New Issue

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This isn't really a new issue, but one that I've had since I bought the car and I want to get to the bottom of it. There's a clicking sound that's coming from under the car. It's not very loud and can only be heard while driving slowly alongside a wall or Jersey barrier with the windows rolled down, or even backing out of the driveway when I'm going slowly enough so that there's no wind or road noise. I got under the car yesterday and had my son turn the rear wheels so that I could see where the noise was coming from. It’s coming from inside the Dynaflow transmission tail shaft near where the speedometer cable attaches. I ran out of time yesterday and won't likely get back under the car until next week, but I'd like to know if anyone on the forum has experienced something like this. The speedometer works fine, nice and smooth, so I'm thinking that maybe all is well with the gear and cable. There's no perceptible play in the drive shaft where it enters the transmission. I'm not concerned that there's something bad going on in there, but I'd like to know what's going on. Any ideas would be appreciated.

 

Jim

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Hmm, you can only hear the click if it reflects off something at speed or when you are under it? Usually, big turns in a large empty parking lot helps to determine differential pinion versus axle noise. Nothing to reflect out there and you think it's the transmission tailshaft. Although speedo is smooth, maybe disconnect the cable down there and take it for a test run.

Parking brake cable not rubbing on anything rotating? When you were under it, was the rear axle dropped? Or, did you support the rear with jack-stands under the axle to simulate ride height?

BTW, your Skylark should have the 2-speed ST-300 transmission.

John

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The click is always there. I mentioned that it's only audible from inside the car when the sound reflects of something only to indicate that it's not very loud. It's audible from under the car while it's on a lift and you rotate the rear wheels. I made no attempt to simulate ride height since the noise is always there. There's no question as to where the sound is coming from, as I used a stethoscope to isolate it to the tail shaft. I initially thought it might have been the front U-joint, but the stethoscope ruled that out. I hope next week to have time to get under there again and disconnect the speedo cable and see what happens. I should have done that while I was under there the first time, but I was running out of time and needed to get somewhere and wanted to take the Buick.

Edited by Machine Gun (see edit history)

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A friend of mine had a somewhat similar "click" at low speeds on an Alfa Balooco GT.  It didn't start until several thousand miles from new.  One Saturday, we did some checking and it sounded like it was coming from the rh front wheel area.  We knew it had an electric speedometer, but as it turned out, the "click" was really coming from the ECM in the rh kick panel.  It was the sensor for the speedometer causing the ECM to make the sound every few feet of travel.  When we found it, we were relieved and amazed.

 

Does your speedometer work well now?  The needle move smoothly?  On the output shaft of the trans, the "drive" gear is usually (at least on later models of GM vehicles) by a metal clip that has an index hole that keeps it in place.  The gear slides over that clip and it stays there.  The "driven" gear is what the drive gear turns that runs the speedometer cable.  Generally, the tailshaft housing is open inside, other than the output shaft, related bushings and seal, and the speedometer gear mechanism.  On second thought, there might also be the transmission governor mechanism in that general area, too., but possibly inside the rear of the trans case.  "Telegraphing" sound?

 

Please keep us posted on your diagnosis

NTX5467

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If you have a chance, I'd check the manual to see if there is an adjustment for the shift linkage.  I'm thinking the park position is misaligned and that is the parking pawl running against it's gear.

 

If not that, I'd be looking at replacing the rear outer axle bearings unless you have proof that they have already been changed. I know, they are not close to the location of the noise but I chased a clicking noise on my 56 for several years before discovering one ball bearing that was galled in the front passengers side hub assembly.  That noise was so elusive!  In your case you know it has something to do with the drive line assembly so it's obvious it's not the front wheel bearing. 

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NTX: The speedometer works well and the needle moves smoothly without bouncing. While that may not entirely eliminate the speedo drive gear, it leads me to believe that the sound is coming from another source. You are correct that the sound may be telegraphing from somewhere front of the tail shaft. I'll have to do a deeper dive over the weekend.

 

John: I will check to see if there's a shift linkage adjustment that may affect the parking pawl, but I doubt that the problem may lie with that. Consider that the sound is present in all gears, and when I checked under the car I had the transmission in Neutral. There would have to be one hell of a linkage mis-adjustment for the parking pawl be be anywhere near being engaged while in Drive or Neutral! Also, the stethoscope detects the sound only at the tail shaft. I held the stethoscope on the end caps of the front U-joint as well as the drive shaft itself while listening for the sound, and there's nothing coming from either of those locations. Of course, until I find the source of the sound I can't completely rule anything out, but based on my initial findings so far I will focus my efforts for the time being on the transmission side of things. As for the rear wheel bearings, I have no idea if they've ever been replaced, but I will give a listen back there as a matter of course. You never know!

 

Thank you both for providing your suggestions. I'll keep you posted.

 

Jim

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Update (sort of). I didn't have as much time to diagnose this as I had hoped, but I did manage to find a few minutes to get under the car last week. All I had time to do was disconnect he speedometer cable in order to verify that the cable isn't where the sound is coming from. It makes a click about every quarter turn of the driveshaft. My next steps, which likely won't happen for at least two weeks, will be to remove the speedometer gear from the tail housing and see if perhaps the gear is making the sound. If not, perhaps the governor would be the next place for me to look. After that, who knows?

 

If I can't pinpoint it after that I'll probably just let let it go until I learn to live with it, or until it gets worse or something blows up. It's not very loud and it doesn't seem to be serious, nothing like a bearing or anything like that. I have two other, more pressing things to attend to right now, like a leaking power steering pump shaft bearing and a pretty good oil leak coming from the passenger side of the engine apparently coming from somewhere above the starter.

 

It's always something. Of course if I didn't like complaining and working on old cars I'd have bought a new Buick!

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Thanks for the update.  

 

Does "the click" disappear with speed or just get fast enough that it's not noticed as much?  On one car we have, I'd noticed "a click" when taking off.  I removed the sometimes-squeeking wheel covers to no avail.  There was also a light vibration when taking off and a vibration at 70mph.  The service writer took it around the block and pronounced "front u-joint".  I was surprised, but it fixed it.  Everything was smooth and quiet after that.  There didn't seem to be any "excess" slack as I'd seen in other u-joint failures.  So just moving the driveshaft might not fully be a good test for u-joint slack.

 

Another wear point in that area is the bushing the driveshaft slip yoke slides against, just In front of the tailshaft housing seal.  Usually, though, when the bushing wears, the seal is not far from leaking.  Just a thought.

 

NTX5467

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On 5/30/2017 at 6:12 PM, Machine Gun said:

NTX: The speedometer works well and the needle moves smoothly without bouncing. While that may not entirely eliminate the speedo drive gear, it leads me to believe that the sound is coming from another source. You are correct that the sound may be telegraphing from somewhere front of the tail shaft. I'll have to do a deeper dive over the weekend.

 

John: I will check to see if there's a shift linkage adjustment that may affect the parking pawl, but I doubt that the problem may lie with that. Consider that the sound is present in all gears, and when I checked under the car I had the transmission in Neutral. There would have to be one hell of a linkage mis-adjustment for the parking pawl be be anywhere near being engaged while in Drive or Neutral! Also, the stethoscope detects the sound only at the tail shaft. I held the stethoscope on the end caps of the front U-joint as well as the drive shaft itself while listening for the sound, and there's nothing coming from either of those locations. Of course, until I find the source of the sound I can't completely rule anything out, but based on my initial findings so far I will focus my efforts for the time being on the transmission side of things. As for the rear wheel bearings, I have no idea if they've ever been replaced, but I will give a listen back there as a matter of course. You never know!

 

Thank you both for providing your suggestions. I'll keep you posted.

 

Jim

When disengaged from park, the pawl only moves a short distance from the gear into which it locks.  It does not rotate 90deg away.  Could be a little out of adjustment and slightly rubbing as the gears go by

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NTX: The click is always there, at all speeds. As I said previously it's not very loud and is only audible at road speed when the windows are down and I'm riding along something that reflects the sound back into the car, like Jersey barrier. There's no vibration at any speed, or any other symptom that might suggest a U-joint problem. I hear nothing with a stethoscope probe placed directly on the U-joint; the sound is only audible through the stethoscope when I hold the probe on the tail shaft. That's why I'm ruling out the U-joint. Hopefully it's not the tail shaft bushing.

 

Jack: You're the second guy to mention the parking pawl. JohnD also mentioned it and I sort of dismissed it, but I should probably take his and your suggestion if I don't find anything wrong with the speedometer gear. I'll have to pull the manual and see how to check the pawl adjustment.

 

I'll update after I get back under there in a week or two.

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Thanks for that additional information and clarification!  I don't think the rear bushing would "click" as it's a rubbing interface.  Generally, if the tailshaft housing seal is not leaking, no issues with the bushing.  If the seal is leaking, the bushing has worn enough to allow the seal to experience more wear than it's designed to have, an both wold need replacement.

 

Holler back when you have more information.

 

NTX5467

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Problem identified and solved this afternoon. I would rather not have replied and let the topic fade from memory, but I said that I'd update you. The short answer is that the noise came from my passenger side front wheel cover! Here's the long answer:

 

I lifted the car up again this afternoon and spun the rear wheels and listened for the sound once again in an attempt to isolate it. I was able to hear it, but it suddenly occurred to me that the sound emanating from the transmission tail shaft didn't seem loud enough to be heard at road speed. I started the car while it was in the air inside the garage, shifted into drive, and slowly released the brake. The wheels spun, but there wasn't the slightest hint of the noise I'd been hearing since Day One of my owning the car. OK, now what?

 

I manually spun the front wheels again, checked the wheel bearings, nothing. I set the car down, backed it out of the garage, and the clicking was there again. I asked my wife to drive slowly out of the driveway while I walked beside the car and heard the sound coming the wheel cover. I removed the cover, road tested the car and for sure the sound was gone. Early on the process I had removed the wheel covers to see if there was anything loose inside them or with the retaining rings, but everything was tight and secure. I throughly checked the offending wheel cover after I removed it today and it was secure as ever. For lack of anything else to try, I readjusted the retaining ring teeth that hold it onto the wheel, although the cover was always very secure on the wheel. That adjustment solved the problem. The only thing I can think of that may account for the issue is that the slight flexing/deformation of the wheel with the weight of the car on it was just enough to have one or more of the wheel cover retaining teeth to make and break contact with the wheel. Whatever, it's fixed. I feel like a numb-nuts.

 

Thank you for all of your suggestions - Jim

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Don't feel too bad Jim.

After driving my Special this past few months, kept hearing a rattling while moving too at slower speeds.

In my case it was the plastic emblem centers in two of my hub caps.

Seems I had put on four caps from a stack of spares I have instead of the good ones I took off her way before and had those put away (you know, believing you will remember where they were when you wanted them again...:rolleyes:).

Easy fix. Swapped them out and presto, no more rattling! ;)

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On 7/4/2017 at 6:36 PM, Machine Gun said:

Problem identified and solved this afternoon. I would rather not have replied and let the topic fade from memory, but I said that I'd update you. The short answer is that the noise came from my passenger side front wheel cover! Here's the long answer: ...The only thing I can think of that may account for the issue is that the slight flexing/deformation of the wheel with the weight of the car on it was just enough to have one or more of the wheel cover retaining teeth to make and break contact with the wheel.

 

Thank you for all of your suggestions - Jim

Should have thought of this since the same thing happened to me years ago with a '68 Tempest. When I bought it had bias ply tires and I replaced with radials when they wore out. Never had a problem with hubcaps making any noise until then but they sure did with radials. Would click and actually rotate so the single cutout in them that was to give access to the valve was no longer where it could be used without popping the hubcap off. Betting you are running radials, right?

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Yep, running radials. I had a problem similar to yours with shifting wheel covers on my radial-equipped '62 Studebaker GT Hawk. Although the GT covers moved they didn't make any noise, while the Skylark cover made noise yet all four stay put.

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Had wheel flex isssues on our '66 Chrysler, with the original bias ply Goodyears.  Might have squeaked some, but the main thing was their turning on the wheel, enough that it seemed it would flex the valve stem too much.  There were small rust residues on the wheel where the "biters' contact it, plus along the edge of the cover where it contacted the wheel, too.  The fix?  A set of same year New Yorker wheel covers (as one of the plastic centers had exited the Newport wheel covers on that same wheel.  I had tried to readjust the retainers and nothing worked.  Finally took the valve stem extensions off the short valve stems and repositioned the wheel cover's valve stem hole away from the valve stem.  No issues with the tire losing air, but easy enough to pup the cover off, if need be.

 

Thanks for the update and resolution of the issue!

NTX5467

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