Wobble and shake

[W.F. Brown- III]

Something new has started with my '48 Plymouth Sedan. When starting out, the car wobbles like one of the tires are out of round. After just a short distance and after up to speed, the wobble disappears. Once the car has warmed up, no more wobble even at low speeds. There is no shimmy or vibration felt in the steering wheel. The tires are properly inflated and show no signs of wear. Any ideas?

[Don Coatney]

Are you running bias ply tires? They have been known to develop flat spots when parked that will disappear after a short drive.

[W.F. Brown- III]

They are bias ply tires, but I don't think the car doesn't stay parked long enough to create a flat spot.

[desoto1939]

Try this fix. Put some old carpet under each wheel when you park the car.  This is helpful when on a cement floor.  This will stop the flat spot. I have had bia ply on my 39 Desoto for 20 + years and my car has always had a rug under the entire car.  I do not ever get a flat spot.  Also was told this at a local museum that has 100K valued cars. They have rug pieces under each tire and all are bia ply cared tires.

 

 

Rich Hartung

desoto1939@aol.com

[W.F. Brown- III]

The car sits in a dirt floor garage, but I'll try the carpet idea. However, if it actually was a tire with a flat spot wouldn't I feel that in the steering wheel?

[desoto1939]

If on a dirt floor then I would put some plywood down first.  The moisture that come up from the floor or dirt is not good for the undercarriage.  The flat spot evens out as the tires start to roll on the pavement and they warm up and the biaply then becomes plyable and the flat spot is removed. 

 

Does not take long for a flat spot to form when sitting. Just think of all the weight on the tires from the entire body and engine.

 

Give it a try and let us know how you make out. It just might be this simple trick.

 

Rich Hartung

[W.F. Brown- III]

Will do. Thanks.

[plymouthcranbrook]

I remember a friend who had nylon tires on his 59 Plymouth and every morning the car shook for the first couple of miles

[W.F. Brown- III]

I've had this car for six years. The tires are the same ones that were on the car when I got it and I park it in the same place as I have for those six years. The wobble just started a couple weeks ago.

[greg g]

Just for the heck of it, pull the dustcap and see if the wheel bearing, maybe needs snugging up.

[deathbound]

I had a low speed wobble, but the car warming up had no effect. I rebuilt the steering box (sector shaft was severely worn), replaced all the rod ends/tie rods...whatever you want to call 'em, replaced drag link, replaced king pins. Afterwards, steering was tight-in a good way and no wobble whatsoever, at any speed. Not saying these issues are your problem, but even a couple may contribute. A visual/wiggle here and there should give you a good idea of the condition of the steering components.

[1940plymouth]

I think you may have mentioned the "Magic" word.  Six years,  the tires are getting older now and the "flat" spot will become more noticeable and as time goes one, each tire will most likely develop one

[dpollo]

If this problem was more noticeable in freezing weather, I'd say one of the tires has water in it.

This can  happen in a carelessly installed tubeless tire  but it would not be likely in a tube type.

[W.F. Brown- III]

The problem only started a couple weeks ago. Nice, dry and warm weather. No problems before, even during the extreme cold we had this winter.

[Plymouthy Adams]

what have you actually tried thus far to rule out common items?  like rotating tires to see if it will move to another location...somewhere you got to play a part in the fix..

[W.F. Brown- III]

This just started a couple weeks ago, so I haven't really done anything yet (other than pay close attention to see if I can determine some kind of "pattern" for the wobble).

After these suggestions, I plan on trying the carpet scraps under the tires first. If that doesn't work, then rotating the tires.

Hopefully, I can rule out the "simple" fix (inexpensive fix), before moving on to having a mechanic check it out.

[W.F. Brown- III]

I just got back from doing a little "experimenting" with the wobble issue on my '48 Plymouth.  I discovered I was wrong about it stopping once the car had sufficiently warmed up and had been driven for several miles.  Previously, the wobble problem was noticed when I started the car and pulled out of the driveway.  What I learned today was that when I first pull out and begin going through the gears, I am moving rather slow (the way the drive enters into the highway plays a part in this).  However, after any other stop, when starting out I tend to go through the gears much faster and build speed much quicker.

 

So, what I did was to pick a nice long and secluded straightaway and do some experimenting.  All this was after the car had been driven several miles and the motor, tires, etc. were sufficiently warmed up.  I discovered, when just barely creeping along in first gear the car had a distinct wobble (real distinct).  There is no "shimmy" in the steering wheel, however.  With tut the clutch in and still just barely moving, the wobble is still there but not quite as bad as under power.  As the speed increases and as I move up through the gears the wobble disappears (or at least is not noticeable any more).

 

I repeated this process several times with the same results.  The slower the speed (like down to almost a crawl), the more the wobble.  The faster the speed, the less the wobble until it is gone.

 

From this experiment, I would think that should discount a "flat spot" on the tires.  The motor/transmission mounts have been mentioned, but I would think that if these were bad it would show not only when moving but when stopped and the motor revved.  The driveshaft issue might be a problem, but I would think the faster it was moving the greater the vibration would be (I could be wrong about that).  The kingpin issue is something I don't have a clue about, and don't have the resources to check myself.

 

Given all this, any further ideas?

I just got back from doing a little "experimenting" with the wobble issue on my '48 Plymouth. I discovered I was wrong about it stopping once the car had sufficiently warmed up and had been driven for several miles. Previously, the wobble problem was noticed when I started the car and pulled out of the driveway. What I learned today was that when I first pull out and begin going through the gears, I am moving rather slow (the way the drive enters into the highway plays a part in this). However, after any other stop, when starting out I tend to go through the gears much faster and build speed much quicker.

So, what I did was to pick a nice long and secluded straightaway and do some experimenting. All this was after the car had been driven several miles and the motor, tires, etc. were sufficiently warmed up. I discovered, when just barely creeping along in first gear the car had a distinct wobble (real distinct). There is no "shimmy" in the steering wheel, however. With tut the clutch in and still just barely moving, the wobble is still there but not quite as bad as under power. As the speed increases and as I move up through the gears the wobble disappears (or at least is not noticeable any more).

I repeated this process several times with the same results. The slower the speed (like down to almost a crawl), the more the wobble. The faster the speed, the less the wobble until it is gone.

From this experiment, I would think that should discount a "flat spot" on the tires. The motor/transmission mounts have been mentioned, but I would think that if these were bad it would show not only when moving but when stopped and the motor revved. The driveshaft issue might be a problem, but I would think the faster it was moving the greater the vibration would be (I could be wrong about that). The kingpin issue is something I don't have a clue about, and don't have the resources to check myself.

Given all this, any further ideas?

[VFFFrank]

Although I wouldn't expect it to correct itself after driving a while, a "tread separation" or rupture of some of the cord will generate the symptoms you describe especially if the shake came on quickly.

If it says"Firestone" on the side, it's more likely to be so. (just my experience/opinion, of course).

Jack it up one wheel at a time, spin 'em and watch for a twist in the tread or have someone follow you and watch for it.

Frank

[Niel Hoback]

Frank has just described exactly what happen to my Goodyears several times.  When you jack it up, put the jack under the differential and idle the engine in reverse while holding a piece of chalk as steadily as you can against the outer sidewalls to mark any wobble.

[deathbound]

Refer to my post above. Any easy and quick check of all the steering components might tell you something. Are any joints loose with excessive play?

[Niel Hoback]

If you don't feel anything in the steering wheel, it's not likely to be front end problem.

[Seaside Pete]

If you don't feel anything in the steering wheel, it's not likely to be front end problem.

 

 

I agree. Generally when it comes to wheels/tires/discs/brake drums etc, if you feel a steering wheel wobble it's the front no steering wheel but foot pedal it's the rear.

 

Pete

[mlozier76]

Have you checked the driveline?  You may have part of your parking brake shoe that broke off, creating an imbalance on the driveline. Sometimes the driveline will be in harmony at higher speeds but not lower speeds and vice versa. 

[Tom Skinner]

Bad U Joints?

Clutch Judder?

[W.F. Brown- III]

I'm beginning to lean towards u joints as being the most likely culprit.