Vibration at freeway speeds
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Joined: Aug 2008
Posts: 62
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From: Bay Area Californina
Vibration at freeway speeds
Hi everyone! Im in the process of resurrecting an 85 vette that has been sitting for 15 years... everyhting has been going good so far, got her running decent (stutters a bit at low end) but thats not my worry anymore. I got her on the freeway this weekend and when i got to about 65 there was a mean vibration throughout the car when i was under acceleration. As soon as i would let off the gas it would go away. Does anybody have any ideas what the problem could be? I put it up on jacks to look for loose U-Joints and found nothing. sombody told me they may be tight from lack of lube... However, i understand that when im wiggling them under the car it doesent compare to the force of the motor under acceleration. I was thinkng i would swap them and cross my fingers, there probably the originals anyways. Im hoping its not a tranny issue, i no the last owner wasnt nice to it 
Any help or suggestions would grrreat!
Thanks,
-Brian
Any help or suggestions would grrreat! Thanks,
-Brian
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Vibration @ ~ 65+ is usually U joints. Quick U-joint check: put the car in park or 1st gear then get out and push/rock the car back and forth really really hard and listen for U joint slop or pops. I'm sure you replaced the 15 year old tires...right? It may be time to check the alignment too so you don't burn up your front tires.
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Joined: Aug 2008
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From: Bay Area Californina
Yea i replaced the tires as soon as i got her running, they were toast! thanks for the idea on the u-joint test ill give it a shot and cross my fingers!
Anybody recommend a drive shaft balance while i have it out?
Anybody recommend a drive shaft balance while i have it out?
Thread Starter
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Joined: Aug 2008
Posts: 62
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From: Bay Area Californina
Im not sure. My assumption would be they would also need replacing since the car has been sitting for so long and had low maintenence from the previous owner as well. Ill get under the car and take a peek, see if there is any wobble or wear at the joints. Thanks!
The vibration really feels like its in the seat which leads me to believe its a rear end or drive train problem, but i welcome all suggestions because im deffinatly not a pro in the corvette scene.
Thanks again
The vibration really feels like its in the seat which leads me to believe its a rear end or drive train problem, but i welcome all suggestions because im deffinatly not a pro in the corvette scene.
Thanks again
Instructor
Joined: Nov 2007
Posts: 108
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From: Waukesha WI
I have the same problem, an 85 as well. You say it runs bad at lower RPM? Check your fuel pressure, you may be running lean, which will cause the car to vibrate on the freeway cause the engine is essensially "misfiring" cause it's not getting enough fuel. That's the problem with mine at least. I've already replaced the fuel pump, now i think it needs a pressure regulator.
Le Mans Master
Joined: Oct 1999
Posts: 6,366
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Vibration @ ~ 65+ is usually U joints. Quick U-joint check: put the car in park or 1st gear then get out and push/rock the car back and forth really really hard and listen for U joint slop or pops. I'm sure you replaced the 15 year old tires...right? It may be time to check the alignment too so you don't burn up your front tires.
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vibration
Check your rear wheel bearings. I had a nasty vibration in my 89. My u-joints were all fine. It was my rear wheel bearings.
Pro
Joined: Jun 2008
Posts: 531
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From: Calgary Alberta
I've been having a very similar sounding issue.
I can feel it very very lightly at lesser speeds, but it becomes a noticable vibration at 120 km/h (75mph) under acceleration, once you pull back a little and settle into a speed, it'll go away by about 50%. This noticable vibration (and relaxation when coasting) can happen at any speed above 75mph.
It just happend to start exactly the same day that I change my rear tires. The "new" tires are well used, but no where close to the ones I took off). Figuring it was the re-used old tires on the back I wasn't worried as they only need to last me another 500 miles (if that)...
Is this something worse I need to look into ?
I can feel it very very lightly at lesser speeds, but it becomes a noticable vibration at 120 km/h (75mph) under acceleration, once you pull back a little and settle into a speed, it'll go away by about 50%. This noticable vibration (and relaxation when coasting) can happen at any speed above 75mph.
It just happend to start exactly the same day that I change my rear tires. The "new" tires are well used, but no where close to the ones I took off). Figuring it was the re-used old tires on the back I wasn't worried as they only need to last me another 500 miles (if that)...
Is this something worse I need to look into ?
Thread Starter
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Joined: Aug 2008
Posts: 62
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From: Bay Area Californina
Thanks for all the good advise everyone! Because of cost i decided to start with a drive shaft balance and u-joints. Already have the joints (and have a fuel pressure tester on order to test the rough running issue). Ill keep the forum updated as things play out over the next few weeks on the hunt for the vibration! Thanks again....
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Joined: Aug 2008
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From: Bay Area Californina
I just pulled out my drive shaft so i can go get it balanced and new u joints installed. I noticed a little play at the transmissions splined shaft (i think its the o-drive unit where the yoke slips in at). Is there usually a little play at this loation? the seal looks in good condition and was not leaking. If you have any input it woulds be great!
Btw, i looked at all my front end joints and rods every thing seems to be ok. since there is no shake in the wheel im starting with the rear.
thanks
brian
Btw, i looked at all my front end joints and rods every thing seems to be ok. since there is no shake in the wheel im starting with the rear.
thanks
brian
Cruising
Joined: Feb 2007
Posts: 13
Likes: 3
From: Los Angeles
vibration problem @ 65 mph
Hi from Istanbul!
I have a 88 with automatic trans ,
I have the same vibration problem which begins at 67 mph under semi-hard accelerations, on really hard acceleration nothing ???
I feel this vibration coming from rear end and I think to change the transmisson output yoke and the U-joint of main shaft as you think to do.
Anothe add info : when the exterior temperature is high , I have more vibration , but now it is cold in Turkey and there is less vibration.
Did you have any positive feedback after chnagind the U-joint ? any experience about that is welcome.
Thank you
I have a 88 with automatic trans ,
I have the same vibration problem which begins at 67 mph under semi-hard accelerations, on really hard acceleration nothing ???
I feel this vibration coming from rear end and I think to change the transmisson output yoke and the U-joint of main shaft as you think to do.
Anothe add info : when the exterior temperature is high , I have more vibration , but now it is cold in Turkey and there is less vibration.
Did you have any positive feedback after chnagind the U-joint ? any experience about that is welcome.
Thank you
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
Check the wheel bearings too, Lift the car and see if you can feel any play there, pushing in at the top and pulling out at the bottom of the tire several times. Slack there can cause vibration too. I just replaced both rear bearing hubs and got rid of alot of vibration. One of my "new" tires is out of round and that causes Some vibration as well. Once the tire heats up some, it lessens. Check those things as well as your U joints just in case. If the vibration is only at highway speed, it is probly U joints as others have mentioned. Hope ya figure it out.
Racer
Joined: Sep 2004
Posts: 323
Likes: 1
From: Muncie Indiana
If you have not replaced the plugs and wires I would guess that what you are getting is a misfire from the spark jumping through the wires. Get it in a very dark place and start the engine and watch for spark jumping to ground. All the other suggestions are possibilities but I would do the easy cheap things before I jumped into just throwing parts and money at it without any clue as to what is actually wrong.
Recently I was complaining to my tire dealer about the balance of the rear tires and he said they were fine. I happened to change the original plugs and wires on my 93 and all of a sudden the car cruises without vibration at interstate speeds.
I hope this helps you save some money.
Recently I was complaining to my tire dealer about the balance of the rear tires and he said they were fine. I happened to change the original plugs and wires on my 93 and all of a sudden the car cruises without vibration at interstate speeds.
I hope this helps you save some money.
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Joined: Aug 2008
Posts: 62
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From: Bay Area Californina
I finally figured out what the problem was!!! It was one of the worst cases, but ended up being easy to test for. As it turned out my torque converter lock out clutch is bad causing a mean chatter when the lock out solenoid enguages. All you have to do to test for this is unplug the four prong connector on the drivers side of the tranny. This will bypass the solenoid, (just like the toggle switch that you can buy to bypass the same thing). Its going to be a PITA fix bc the tranny needs to be pulled, but you gotta do what you gotta do right? Im curious if this was the problem for a few of the other forum members that had the same issues occurring. Let us know....
Thanks for all the feedback ill be in touch when i get the car apart!
Brian
Thanks for all the feedback ill be in touch when i get the car apart!
Brian