Cyclic Vibration - what is it?
Thread Starter
Instructor
Joined: Aug 1999
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From: Chandler AZ
Cyclic Vibration - what is it?
When I get between 70 & 80MPH, my whole car starts to vibrate. The vibration starts and stops with a constant frequency. If I disengage the clutch it still vibrates, so I was thinking balance, tracking, or shocks. I had the tire balance done - it did not fix the issue.
So my question is, tracking? Shocks? Or something else.
If it's tracking, what are some good tracking spec. I had some pretty aggressive tracking done last time and that might be the problem. I want to get some negative camber for better cornering, but that's about it.
So my question is, tracking? Shocks? Or something else.
If it's tracking, what are some good tracking spec. I had some pretty aggressive tracking done last time and that might be the problem. I want to get some negative camber for better cornering, but that's about it.
Team Owner
Joined: May 2001
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Take your car to any service shop that has a Hunter 9700 road force balancer and go from there. At least that will pinpoint for sure if it's a tire and/or a wheel assembly. If they are eliminated, then consider drive shaft, CV axle assemblies, etc. Forget shocks; they don't rotate.
HTH,
Robert
HTH,
Robert
Thread Starter
Instructor
Joined: Aug 1999
Posts: 235
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From: Chandler AZ
I have hardened half shafts put in with the new 4:10 rear end.
Do the main drive shafts really warp? I'm probably somwhere in the range of 500HP at the crank - I still need to get a final tune and a dyno.
Do the main drive shafts really warp? I'm probably somwhere in the range of 500HP at the crank - I still need to get a final tune and a dyno.
Melting Slicks
Joined: May 2000
Posts: 2,498
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From: Brentwood TN
Originally Posted by ElanMike
Do the main drive shafts really warp?
My bet is on the torque tube.
Charlie
Thread Starter
Instructor
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From: Chandler AZ
I was thinking about this again last night. If it is the torque tube, and the gear box is in the rear, then the tube will rotate with engine speed. Therefore, when i disengauge the clutch, I would expect the vibration to stop. I would also get the vibration when the tube reaches the right rotational speed in other gears, at different speeds. Wouldn't this point to wheels or half-shafts?
Advanced
Joined: Jun 2006
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From: Durham NC
I think you can eliminate the cv's/halfshafts as the source of your problem. I can't think of anything that would suddenly start a vibration in a certain speed range.
You haven't bent a wheel have you?
You haven't bent a wheel have you?
Melting Slicks
Joined: May 2000
Posts: 2,498
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From: Brentwood TN
Originally Posted by ElanMike
I was thinking about this again last night. If it is the torque tube, and the gear box is in the rear, then the tube will rotate with engine speed. Therefore, when i disengauge the clutch, I would expect the vibration to stop. I would also get the vibration when the tube reaches the right rotational speed in other gears, at different speeds. Wouldn't this point to wheels or half-shafts?
I would tend to discount a bent wheel because I would HOPE the dude that balanced the wheels would notice a wheel bent badly enough to cause the vibration, especially since the bent wheel should have replicated the vibration.
I think your suspicion about one or both half shafts takes on more credence. And with the horse pressure your engine puts out and with even OEM wienies, a hard launch is absolutely enough to scrink the tubes if the tires get a good grip on a hard 1-2 shift.
It'll be interesting to know what you ultimately find out.
Charlie
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Team Owner
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From: At the beach in little Rhody
If you mean the driveshaft within the torque tube, it rotates with the wheel speed since the clutch is in front of it. So disengaging the clutch only took the engine/clutch out of the spinning parts at speed.
Melting Slicks
Joined: May 2000
Posts: 2,498
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From: Brentwood TN
Originally Posted by vettenuts
If you mean the driveshaft within the torque tube, it rotates with the wheel speed since the clutch is in front of it. So disengaging the clutch only took the engine/clutch out of the spinning parts at speed.
Charlie
Intermediate
Joined: May 2006
Posts: 27
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From: Hiram GA
Cyclical vibration
ElanMike,
I had the same issue a couple of months ago. I bought some aftermarket ZO6 wheels, and then had then mounted and balance at Butler Tire here in Georgia. I think balancer indicated above was utilized? But, what I do know is the wheels/tires were speed balanced on the car. Up to 155 mph no problem. Took the car in to Chevrolet dealer for brake service and driving home 60-75 mph harmonic vibration kicked in. Took the car back to Butler tire had then balanced again and lugs torque to spec no problems with vibration since. Start with balancing, lugs torque to spec and then brakes (least expensive to fix), and then like stated above drivetrain "torque tube".
I had the same issue a couple of months ago. I bought some aftermarket ZO6 wheels, and then had then mounted and balance at Butler Tire here in Georgia. I think balancer indicated above was utilized? But, what I do know is the wheels/tires were speed balanced on the car. Up to 155 mph no problem. Took the car in to Chevrolet dealer for brake service and driving home 60-75 mph harmonic vibration kicked in. Took the car back to Butler tire had then balanced again and lugs torque to spec no problems with vibration since. Start with balancing, lugs torque to spec and then brakes (least expensive to fix), and then like stated above drivetrain "torque tube".
Pro
Joined: Aug 2004
Posts: 575
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From: Richmond Hill Ontario
Cyclical vibration
If you've had your tires balanced with the road force machine and they couldn't find anything wrong with the tire or rim I would eliminate this from your list provided you haven't lost a wheel weight. There's also the possibility that you've spun the rim within the tire after you had your tires balanced and that could definitely cause an unbalanced condition. Definitely start with the easiest things to fix first before you get into the torque tube or rear half shafts. Make a list starting from the simplest things that could be causing your issue and work your way down. I'd personally go to either a reputable shop or dealer to have someone drive your car and give their opinion. Try a couple of different places and see if you can get a concensus. With the power you're pushing you can expect to kill whatever is the weakest link in the drivetrain.
Good Luck and let us know.
Good Luck and let us know.
Le Mans Master
Joined: Feb 2006
Posts: 5,267
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From: Phoenix AZ
I know this may sound dumb, but I have a Mercedes with aftermarket wheels. The front wheels were hogged out in the hub area to fit a previous BMW. When I put the wheels on, there was slop between the hub and hub hole in the wheel. Now you would think the lugnuts being tapered would center the wheel......only if you hand tighten very carefully while rotating/shaking the tire. I was getting some harmonic type action and it turned out the rims were not perfectly centered. Maybe the last guys just slammed the first lugnut on with the impact and kept going with the wheel slightly off?
Melting Slicks
Joined: Dec 2003
Posts: 3,315
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From: Near Jacksonville Fl.
Originally Posted by cruisemon
You are correct; the drive shaft is suspect. I managed to get myself off in the weeds about where parts and thingies are. Thanks.
Charlie
Charlie
A twisted drive shaft will start to vibrate at a much lower speed like around 40 mph and continue to get worse the faster you go. The same holds true for axle shafts.
I would look at the tires and wheels for balance and run out, remember they rotate at different speeds hence the cyclic vibration.
And yes I also have this problem too, one thing that does come to mind is if you have ever had the torque tube removed or the engine did the tech use the proper procedure to align the torque tube?
Racer
Joined: Mar 2006
Posts: 270
Likes: 0
From: los altos ca
Now that i think about it the vibration came after my 505a's, I had put these on at the same time as other suspension mods so i had suspected other components first. I also remember a time when the vibration seemed to stop. Which also haha now that i think about it was when i had taken the wheels off and put them back on. I took them off a third time and now the vibration came back.....My conclusion obviously is that I mounted the wheels improperly as someone suggested. I wish i could say for sure, but the car is on all fours right now and will not be done for another week......I will also get my wheels balanced to make sure its not a bent rim, haha a curb hit my rim recently. Ill let anyone interested know my results as soon as i can
Last edited by Ducati749; Nov 25, 2006 at 01:37 PM.
