Vibration after stopping...
Thread Starter
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
Vibration after stopping...
New here, but have had a couple vettes in the past (C4/C5). This is my first foray inot the C3 corvette, though.
This summer, I picked up a minor project car (79 C3) - engine runs nice, body needs minimal attention, interior needs some replacement parts...
In the last 2-3 weeks, I've noticed a pretty strong vibration when pulling up to stop (like at a light or stop sign) - the vibration stops if I shift into neutral or park. My gut reaction is this is probably the driveshaft or a U Joint - anyone have experience on this problem that I can take advantage of?
This summer, I picked up a minor project car (79 C3) - engine runs nice, body needs minimal attention, interior needs some replacement parts...
In the last 2-3 weeks, I've noticed a pretty strong vibration when pulling up to stop (like at a light or stop sign) - the vibration stops if I shift into neutral or park. My gut reaction is this is probably the driveshaft or a U Joint - anyone have experience on this problem that I can take advantage of?
Team Owner
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2020 C3 of the Year Finalist - Unmodified
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...could also possibly be an unbalanced driveshaft, or the driveshaft front yoke is very worn allowing movement of the driveshaft while going forward and driving. Another thing to check is the rear trans mount for looseness or wear.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
So your saying if you pull up to a stop and its vibrating and you shift into park the vibration goes away ?
What happens if you just sit there with your foot on the brake and at a complete stop ?
(I'm wondering about chattering clutches. )
What happens if you just sit there with your foot on the brake and at a complete stop ?
(I'm wondering about chattering clutches. )
Thread Starter
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
If I pull to a stop, hold my foot on the brake it vibrates. It might sound odd, but it won't do this until the car has been driven for a little while and is warmed up (a couple miles or so). If I'm just pulling out of the driveway, it does not appear do it.
After driving, and I stop with the car in Drive, the vibration shows up.
If I drop it from Drive to Neutral, it goes away - same thing if I go into Park.
I did just now find that my exhaust pipes were a little loose (after market side exhaust, the brackets needed tightened up), making the overall vibration feel worse than it should. I just tightened those up, and the overall vibration reduced when driving/stopping - but it is not gone.
I'm open to any suggestions, so I can compile a list of things I need to check out.
After driving, and I stop with the car in Drive, the vibration shows up.
If I drop it from Drive to Neutral, it goes away - same thing if I go into Park.
I did just now find that my exhaust pipes were a little loose (after market side exhaust, the brackets needed tightened up), making the overall vibration feel worse than it should. I just tightened those up, and the overall vibration reduced when driving/stopping - but it is not gone.
I'm open to any suggestions, so I can compile a list of things I need to check out.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
If the 'vibration' goes completely away when you are at a full stop...in any gear range...it is probably a bad U-joint in the driveshaft or one of the half-shafts. If [when completely stopped] the car vibrates in Drive (1,2, or D) or in Reverse, but not in Park and Neutral, you have some mechanical problem with the transmission. It could just be a broken or backed-out bolt mounting the torque converter to the engine; but it also could be a bad bearing internal to one of the clutch packs inside the tranny case. You can check the T/C bolts by removing the lower inspection cover and bumping the engine over.
Burning Brakes
Joined: Nov 2005
Posts: 1,137
Likes: 51
From: Cartersville GA
What are the RPM's running when your stopped, and when you drop out of gear? Seems the idle at least may be too low, and since it does this when it warms up would lead me to think the automatic choke has kicked off allowing the RPMs to drop.
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Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
OK not diff clutch chatter. As others have said check for rough idle. If you have a miss the engine will run rough and vibrate. I always take a quick visual check of the water pump and fan (in gear) just to make sure its not one of them or a combination of both. When the engine is off see if the pump is loose by trying to wobble the fan back and forth.Check your motor mounts and trans mount. The drivers side mount is the one that breaks but I had a car in that bubba swapped a broken drivers side for the passenger side and it was so wore out that it was metal to metal.
Thread Starter
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
Wow - great feedback.
I have not had time to work on the car tonight, but will definately start running down the list this weekend.
I'll start with the rough idle - but to listen and watch the engine in park, it looks/sounds pretty good. Still, it's aplace to start.
I have to check, but believe I'm idling around 7 or 8K RPMs at idle in P or N. I'll double-check that, and what happens when I shift inot gear, so don't hold me to those numbers yet.
From there, I'll crawl back under the hood and underneath to inspect pulleys, motor mounts, etc.
Thanks to all of you for the ideas - This is great help.
Jim
I have not had time to work on the car tonight, but will definately start running down the list this weekend.
I'll start with the rough idle - but to listen and watch the engine in park, it looks/sounds pretty good. Still, it's aplace to start.
I have to check, but believe I'm idling around 7 or 8K RPMs at idle in P or N. I'll double-check that, and what happens when I shift inot gear, so don't hold me to those numbers yet.
From there, I'll crawl back under the hood and underneath to inspect pulleys, motor mounts, etc.
Thanks to all of you for the ideas - This is great help.
Jim
Burning Brakes
Joined: Nov 2005
Posts: 1,137
Likes: 51
From: Cartersville GA
For my '69 w/auto, in drive is 600 RPM, in P or N is 900 RPM. A couple of other items to check are the plug wires to be sure they are all good, and check your vacuum. It's possible you have a vacuum leak. If you don't have a vacuum guage, get one. They're not expensive and are one of the best diagnostic tools you can have.
I also had a problem when my power valve in my carb went bad (holley) and it was dumping too much fuel into the engine. Good luck, I hope you find the problem.
