Vibration as revs build
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Vibration as revs build
When I'm accelerating a vibration starts around 3000 rpm and increases as the revs do. I can feel it through the shifter and car as I go through the gears. I've seen a few comments on the forum about the drive shaft getting out of balance, or when universals have been replaced. How would a drive shaft get out of balance? It's a pretty solid piece of metal. Is it possible the shaft is slightly off center causing this symptom? I don't know when the universals were last replaced but they look to be in good shape. What did you guys do to fix this kind of problem?
Thanks in advance, Glenn
Thanks in advance, Glenn
Instructor
Joined: Dec 2005
Posts: 181
Likes: 0
From: East Aurora NY
First isolate it. Drive the car up to you feel the vibration. push the clutch in and coast letting the engine fall back to idle. if it is still there then it is drive train. if the vibration goes away then it is engine or harmonic balancer related. I once had a 67 Chevelle that had the same kind of problem. I found out that a balance weight had fallen off the drive shaft. Took it in, balaced it, what a differance. Good luck and let me know how you made out. 
Tom
Tom
Instructor
Joined: Dec 2005
Posts: 181
Likes: 0
From: East Aurora NY
I don't know where you are but I do know that Fleet maintenance is nation wide. Possibly an area Napa rebuild shop. Someone in your area has a business to work on large truck and car u-joint replacement and driveline balancing.
Tom
Tom
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Ok, had the vette out a lot this weekend and believe the vibration is from the engine. The harmonic balancer will be the first thing I'll replace. Besides the harmonic balancer what else might cause this kind of vibration?
Also, I put regular instead of premium (3 gals) just to see how the engine ran and got pinging under load. I fiddled with the timing a bit to try and get rid of it but still pinged. Based on this I'm assuming that my compression is at least 10 to 1 and will have to stick with premium. I figure if it's 9 to 1 I 'd have no problem with reg gas. Opinions?
Thanks, Glenn
Also, I put regular instead of premium (3 gals) just to see how the engine ran and got pinging under load. I fiddled with the timing a bit to try and get rid of it but still pinged. Based on this I'm assuming that my compression is at least 10 to 1 and will have to stick with premium. I figure if it's 9 to 1 I 'd have no problem with reg gas. Opinions?
Thanks, Glenn
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Motor' s got anly about 10-11k on it. Runs great otherwise. Several previous owners were mechanics and changed fluids religiously including the one who put the engine in. My mechanic (vette guy has owned 11 of em) says the same possibilities re; vibration, harmonic balancer or drive shaft. I'll keep what you said in mind though and see what my mechanic says about a possible bad rod. Engine itself makes no other (bad) types of sounds except fot the pinging w/reg gas. No smoke at start up, nothing.
Glenn
Glenn
3rd Gear
Joined: Apr 2008
Posts: 3
Likes: 0
Did you ever get the vibration fixed? I am having the same problem and trying to figure out what it might be. When it hits a higher rpm then the vibration happens. The car still runs great, but it would be nice without the vibration.
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Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Do you get the vibration when stationary in neutral, or only when driving? This may help you isolate it as to engine only or drive train. With my situation it vibrated either way.
Good luck and keep us posted.
Glenn
3rd Gear
Joined: Apr 2008
Posts: 3
Likes: 0
The vibration happens only when its about time to shift (not in idle), I want to say the rpm is around 2700 to 3000. The vibration is strongest with the first gear to second gear transfer, after that it there is less vibration changing gears.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If the engine vibrates at 3000 rpm and higher, it should do so in neutral and parked in your driveway. If so, just remove one accessory belt at a time to determine if any of your accessories (A/C, alternator, A.I.R. pump, P/S pump, etc.) is the 'culprit'. If you have all of them off [yes, you can run it that way for a short time], and you still have the problem, it is MOST likely a bad harmonic balancer or an out-of-balance flywheel. There are other 'internal' possibilities; but I would think a bad connecting rod would knock. Please don't disassemble your engine before you know you have to.
Drifting
Joined: Oct 2004
Posts: 1,259
Likes: 7
From: Ontario
If you have a centerforce pressure plate that is likely the cause. The weights can get stuck off to the side. Vibration from that problem typically starts at 2500-3000 and changes with RPM not speed. Sometimes it smooths out above 4000. If you have a centerforce and RPM sensitive vibration start there. Not fun to check or fix since you will be pulling the trans. So suggest you check the easier items first like some of the above suggestions... but you are likely pulling the trans. It took me two years to track down mine.
Last edited by Retro78; Nov 21, 2008 at 01:34 AM.
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That's a possibility. Also a bad transmission mount or the angle of the driveshaft is off.Also check your exhaust clearances. RPM related vibrations can be caused by the exhaust hitting the frame.
Last edited by capevettes; Nov 21, 2008 at 07:07 PM.
