Engine vibration
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Team Owner
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SPARTAN
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Engine vibration
About to start the pre-season work on my car. #1 on the list is the engine vibration that developed last year. 
Happens at about 3000-3500 rpm, any speed, any gear, clutch in or out. So it's definitely on the engine side of things.
What are the odds of the flywheel/clutch being out of balance? This happened after I installed the 5-speed trans. So that's a possibility. I had the old flywheel resurfaced, but it looked just fine.
Going to run down the whole list though...
Compression Check
Leakdown Test
Valve lash set & spring check
The car is running strong and not missing, so I'm somewhat doubtful that it's one of those things. Really wondering about that flywheel...
Happens at about 3000-3500 rpm, any speed, any gear, clutch in or out. So it's definitely on the engine side of things.
What are the odds of the flywheel/clutch being out of balance? This happened after I installed the 5-speed trans. So that's a possibility. I had the old flywheel resurfaced, but it looked just fine.
Going to run down the whole list though...
Compression Check
Leakdown Test
Valve lash set & spring check
The car is running strong and not missing, so I'm somewhat doubtful that it's one of those things. Really wondering about that flywheel...
Race Director
Joined: Sep 2002
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From: San Diego - Deep Within The State of CONFUSION!
First thing to replace is the Harmonic Balancer. Then check the clutch or torque convertor. The flywheel, if a standard trans, is not going to go out of balance. But a torque convertor can throw a weight and shake like heck.
My money is on the balancer though.
My money is on the balancer though.
Le Mans Master
Joined: Jan 2004
Posts: 8,295
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From: one night in Bangkok you are never lonely
After rebuilding my car I had a vibration even sitting in the driveway when revving the engine. I removed the 4 speed and started it up(no vibration) After inspecting the trans I noticed the trans pilot shaft was messed up so I sent the pilot shaft to the machine shop to true it up and had them machine a new pilot bushing with a smaller hole to match the re machined shaft. Well that took care of that vibration. You may want to check that your pilot shaft matches the pilot bushing, if it is smaller there could be a vibration as it is turning our of sink.. 
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SPARTAN
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Hadn't thought about the pilot bearing, but I seriously doubt that's an issue. I have a Ford to Chevy conversion pilot roller bearing.
Thinking about the trans input shaft here..... looks like I need to pull the trans and see if it does the same thing. What do you mean when you say the pilot shaft was "messed up"? I can't think of what could be wrong with it.
Thinking about the trans input shaft here..... looks like I need to pull the trans and see if it does the same thing. What do you mean when you say the pilot shaft was "messed up"? I can't think of what could be wrong with it.
Burning Brakes
Joined: Aug 2004
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From: roanoke va
i have had a bad piolt bearing before. the only time i noticed a vibration was when you shifted the car rough. when the vibration started you could push in the clutch and the disc and input shaft would recenter itself and then the vibration would be gone. if the problem started i would suspect a bad balance job on the pressure plate or clutch plate. did you install a new one when you changed the trans. about the only way to check this is pull the trans. start car with clutch installed then pull off the clutch and pressure plate and recheck. you might look at the harmonic balancer to see if it has sliped as said before it would be easy to check first but i would suspect the pressure plate.
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SPARTAN
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This is clutch in or out, so it could well be the pressure plate being out of balance a bit. I'll have a look-see at the balancer, but then it looks like the trans is coming out. Whee!!!
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SPARTAN
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Got a first look at it tonight. Not a real clue how to check a balancer. Anyone with sugggestions? I checked the timing to see if the balancer hub was maybe moving. Timing looked pretty much right where it should be (13deg BTDC).
Vibration is pretty strong (I've felt much worse with a driveshaft imbalance) and peaks in that 3000-3500 range.
Seeing as how the balancer is a little easier than the trans, I might pick up a new one just for the heck of it. I sure have a feeling I'll be pulling the tranny though.
Vibration is pretty strong (I've felt much worse with a driveshaft imbalance) and peaks in that 3000-3500 range.
Seeing as how the balancer is a little easier than the trans, I might pick up a new one just for the heck of it. I sure have a feeling I'll be pulling the tranny though.
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Melting Slicks
Joined: Mar 1999
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From: Apex NC
Dave, if the vibration is there with the clutch in or out, then it would eliminate the driveshaft or input shaft as the culprit. With the car in gear and the clutch pedal depressed, the input shaft will not be turning.
I think you're on the right track with the pressure plate or flywheel being out of balance. No reason to think that the balancer mysteriously went bad at just the exact time that you did the clutch and tranny work.
Good luck!
Shannon
I think you're on the right track with the pressure plate or flywheel being out of balance. No reason to think that the balancer mysteriously went bad at just the exact time that you did the clutch and tranny work.
Good luck!
Shannon
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SPARTAN
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That's the thing....I don't recall if it was completely concurrent with the trans swap. Seems to be that it was, but I didn't drive it very hard for quite a while, so who knows. 
Well, I'll be done with some other projects this saturday, so I should have more time to tackle it and see for sure.
Did do a compression check for the hell of it tonight though
roughly 155-170 in all cyls. Not bad.
PS: Harmonic Balancers are more expensive than I thought!
Well, I'll be done with some other projects this saturday, so I should have more time to tackle it and see for sure.
Did do a compression check for the hell of it tonight though
roughly 155-170 in all cyls. Not bad.PS: Harmonic Balancers are more expensive than I thought!
Last edited by ddecart; Apr 18, 2005 at 10:41 PM.
Le Mans Master
Joined: Jan 2004
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From: one night in Bangkok you are never lonely
Originally Posted by ddecart
Hadn't thought about the pilot bearing, but I seriously doubt that's an issue. I have a Ford to Chevy conversion pilot roller bearing.
Thinking about the trans input shaft here..... looks like I need to pull the trans and see if it does the same thing. What do you mean when you say the pilot shaft was "messed up"? I can't think of what could be wrong with it.
Thinking about the trans input shaft here..... looks like I need to pull the trans and see if it does the same thing. What do you mean when you say the pilot shaft was "messed up"? I can't think of what could be wrong with it.
Sorry to get back on this after a time been traveling to the states. What I found on my 4 speed was the pilot shaft end that enters the bushing looked like someone had hamwered on it. so it was not round.
I hope you find your problem soon?
Safety Car
Joined: Aug 2000
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From: San Antonio TX
Diagnose the easy, no cost stuff first. Things like the accessory drive belts being loose can set up a vibration. It could also be the water pump or the fan clutch. Remove the drive belts and run the engine to see if the vibration goes away. It could also be a broken engine mount or something, like the exhaust, contacting the frame. A misfire or cylinder imbalance can also cause a vibration.
Rotating imbalances cause really wicked vibrations and will always get worse with rpm since you're dealing with centrifugal forces, which is why I'd put little time or effort into working these as primary causes first.
There's no point in getting to the harder, more expensive stuff until you rule out the more common causes.
Rotating imbalances cause really wicked vibrations and will always get worse with rpm since you're dealing with centrifugal forces, which is why I'd put little time or effort into working these as primary causes first.
There's no point in getting to the harder, more expensive stuff until you rule out the more common causes.
