1979, vibration between 48 - 60 MPH
Thread Starter
Intermediate
Joined: Oct 2016
Posts: 31
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1979, vibration between 48 - 60 MPH
Looking for good input. I get a vibration, primarily through the steering wheel at about 48-60 MPH. It seems more intense when I press the accelerator and practically fades away when I let off and coast. All 4 tires are new. Balanced when installed and I recently had them re-balanced by my own mechanic. He said he thinks 3 of the wheels are out of "true" as they appeared slightly wobbly on the spin balance. He suggested taking the wheels off and sending them out to a company that straightens rims on cars, including high end cars. Apparently, they put the rims on a press. These are original rims, 39 years old. The car has 45K miles. While worth a shot, what are the odds this car has 3 bent (out of true) rims?
I've been thinking motor mounts or other front end components. It has a new power steering booster, new water pump, all accessory pulleys were re-aligned a few thousand miles back.
I hate the guessing game but the fun of driving it is slipping away.
Thanks to all.
I've been thinking motor mounts or other front end components. It has a new power steering booster, new water pump, all accessory pulleys were re-aligned a few thousand miles back.
I hate the guessing game but the fun of driving it is slipping away.
Thanks to all.
Race Director
Joined: Apr 2003
Posts: 19,352
Likes: 654
From: Tampa, Florida
Drop it in neutral while the vibration occurs.. Does the vibration go away? If it does its more than likely a drivetrain issue.
Swap wheels front to back. Does it go away? If not swap them back where they were then swap left to right.
Its a process of elimination.
Swap wheels front to back. Does it go away? If not swap them back where they were then swap left to right.
Its a process of elimination.
Le Mans Master
Joined: Apr 2008
Posts: 9,435
Likes: 239
From: Powassan ON
I've been chasing a similar vibration.
New trans, all new ujoints and new rear wheel bearings. New tires coming next spring. Will check for wheel runout then.
I think (and hope) it's not a diff issue. It's full of new lube and modifier. I really don't want to tear into it again.
New trans, all new ujoints and new rear wheel bearings. New tires coming next spring. Will check for wheel runout then.
I think (and hope) it's not a diff issue. It's full of new lube and modifier. I really don't want to tear into it again.
Racer
Joined: May 2018
Posts: 297
Likes: 43
if its suspension related the vibrations will not fade when not under throttle, the issue is either a motor or trans mount, a sway bar link, or the wheel alignment possibly a wheel bearing but that is unlikely because if it were a bearing problem would be worse at lower rpm. so im leaning towards alignment.
Thread Starter
Intermediate
Joined: Oct 2016
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I've moved the tires rear to front but not left to right. Before doing that i'll need to check to see if tires have counter-spin precautions on the side walls.
Thanks.
Thread Starter
Intermediate
Joined: Oct 2016
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My mechanic who suggested out of true rims theorized that the issue was harmonic and tuned to certain speeds. But, both excellent suggestions. Thanks.
Last edited by seafox210; Sep 4, 2018 at 01:45 PM.
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Thread Starter
Intermediate
Joined: Oct 2016
Posts: 31
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i vibrations will not fade when not under throttle, the issue is either a motor or trans mount, a sway bar link, or the wheel alignment possibly a wheel bearing but that is unlikely because if it were a bearing problem would be worse at lower rpm. so im leaning towards alignment.
Le Mans Master
Joined: Apr 2008
Posts: 9,435
Likes: 239
From: Powassan ON
I'VE DEFINITELY THOUGHT MOTOR MOUNT SINCE IT FADES WHEN I LET OFF THE ACCELERATOR. NO TELLING WHEN IT WAS LAST ALIGNED; BUT WHEN I REPLACED ALL 4 TIRES (2 were actually original) LAST YEAR I DIDN'T NOTE ANY UNUSUAL TREAD WEAR ON THE FRONT RUBBER, JUST DRY ROT FROM AGE. THANKS.
"Orginal to when you bought the car? Or original to the car at date of manufacture?
First thing is get good tires. Old tires may be bias ply with a flat spot, but then it would shake at all speeds. look for motor mounts. Maybe crumbled and fell out. In my opinion if its a motor mount the fan would more than likely be hitting the shroud. Any sign that the fan is hitting the shroud?
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
Had similar problem. It was the adjustable knuckle that the power steering ram was hooked to the tierod with. Accelleration unloadedi it and caused a wobble. Lettingboff caused it to settle back into the cup.
Thread Starter
Intermediate
Joined: Oct 2016
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"Orginal to when you bought the car? Or original to the car at date of manufacture?
First thing is get good tires. Old tires may be bias ply with a flat spot, but then it would shake at all speeds. look for motor mounts. Maybe crumbled and fell out. In my opinion if its a motor mount the fan would more than likely be hitting the shroud. Any sign that the fan is hitting the shroud?
First thing is get good tires. Old tires may be bias ply with a flat spot, but then it would shake at all speeds. look for motor mounts. Maybe crumbled and fell out. In my opinion if its a motor mount the fan would more than likely be hitting the shroud. Any sign that the fan is hitting the shroud?
Thread Starter
Intermediate
Joined: Oct 2016
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that makes some serious sense! Will bring that up to my guy, next week. Thanks!
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,509
From: Little Rock AR
Had a '72 Impala that would vibrate the front end at speed. You could feel it in the steering wheel. Thought it was shocks but ended up being a front coil spring had a broken a coil near the bottom end. I put a twist-in aluminum spacer block in there between the remaining coils and the vibration went away.
It was just a junky winter car for me - no judgement.
It was just a junky winter car for me - no judgement.
Advanced
Joined: Jul 2018
Posts: 65
Likes: 9
From: Memphis, TN
When I first got my '79 I had a rough vibration through almost this exact same speed range - replacing the 14 year old tires (and more likely the balance on the new ones) fixed it. Wheels could be it
Race Director
Joined: Apr 2003
Posts: 19,352
Likes: 654
From: Tampa, Florida
i'll try the neutral drop, easy. My letting off the gas and coasting makes it all but disappear. Same effect as neural drop?
I've moved the tires rear to front but not left to right. Before doing that i'll need to check to see if tires have counter-spin precautions on the side walls.
Thanks.
I've moved the tires rear to front but not left to right. Before doing that i'll need to check to see if tires have counter-spin precautions on the side walls.
Thanks.
Thread Starter
Intermediate
Joined: Oct 2016
Posts: 31
Likes: 0