First track event with the car yesterday at Laguna Seca. Everything worked great except I noticed a pretty severe vibration starting at 2500 rpm, lasting until about 3000 rpm. I would describe as more of a buzzing vibration, high frequency. Definitely could feel it through the shifter.

This is what I tried when I was there to narrow it down:

Speed: moving or not, it didn't matter, only RPM.
Clutch: Clutch engaged vs disengaged, no difference.
RPM: 2500-3000 is where it is active.

Mods on car:
A&A Supercharger, V2
LG Super Pro Long tube headers and X pipe, Borla stingers

Conclusions on my end:
Harmonic balancer: ( I notice a slight wobble at idle on the original GM balancer)
Headers: Could be caused by the headers rubbing or touching on something, I will check this out.

What else? Torque tube? I figured I would write that off as it is not speed dependent at all.

Thanks for any input.

 

Not sure about your logic on the TT. It's RPM is the same as engine RPM except when you disengage the clutch and then it is being driven from the transmission if you are at moving.

 

I am not sure if the TT is rotating while the car is not moving, or with the clutch engaged/disengaged?

If it is, then I assume it could be related to the issue, but I wasn't sure.

 

TT speed depends on gear and moving, so if always 2500-3000 could prob rule out drivetrain from clutch disc back. Balancer is possible and check all pulleys. When did it start... check what you touched last.

 

Have you changed the clutch and or fly wheel??? That was my very first diagnosis. If not,, more diagnosis will need to be explored.

I agree... If you are stopped and in gear with the clutch DEPRESSED,, The TT prop shaft is NOT moving.

 

I got the car in June last year, I have mainly been working on suspension, seats, harness etc since then, so it has not been driven much.

It wasn't until I drove it this weekend I noticed the vibration, chances are that it could have been there the whole time.

It does have a clutch, that was installed in 2010, at the same time the TT was rebuilt. I have receipts from the previous owner getting this done.

I am going to check the exhaust as that would be the most obvious thing, but beyond that I am somewhat short on ideas except the HB.

What is the best way to diagnose the flywheel/clutch?

 

I just looked at the invoice, it has a TPS Chromoly fly wheel along with a TPS clutch. It was all installed 2010.

I wonder if this is where my issue is..

It doesn't say anything about balancing the clutch and fly wheel on the invoice. I suppose I could drop the clutch inspection cover, and go to town and try a hot balance by adding washers to the PP bolts?

Any other ideas would be appreciated.

 

Before you start altering things, try to isolate the vibration cause.
With the car at rest, put the car in neutral. Rev the engine to the rpm range that seems the worst. Put your hand on the shift ****. Then keep revving at that rpm and depress the clutch pedal. Are the vibrations still present with the clutch pedal depressed? if so, the propshaft is not spinning, so it's not the source of your vibrations, and it could be a clutch balance issue. If the vibrations go away with the clutch pedal depressed, then something in the driveline AFTER the clutch could be the culprit.

And it's the propshaft that spins, not the torque tube. I'm sure you know that though.
If in fact you narrow it down to the clutch and want to try an in-car balance, its' not that difficult to do.

 

Not true. With the clutch engaged the engine and TT are at the same RPM.

 

With clutch in, it is true.

 

I agree as I had already said in post #2. However, you did not clarify that in your statement. I am just trying to keep the OP from being confused on how the TT operates under different conditions.

 

Thanks for all the input! I am trying to figure out how to rule out the TT (prop shaft), so that I can isolate each rotating assembly's separately on the clutch side of the engine.

Sounds like clutch engaged, car not moving, but in gear will be the best way?

 

In N rev up w/ clutch out, then clutch in keeping rpms steady... if the vibes are constant has something to do with engine, fw, pp.
Is the balancer pinned... if not you could start there, because something should do anyway with SC.

 

If it were me I would disengage the clutch so when you start the car the TT will not spin/rotate. Then start the car and bring the RPMS up to your desired range with the clutch still disengaged and see if you have the vibration.

I would do this in Neutral just in case your foot were to slip off the clutch petal by accident. Safety First.

 

Update on this issue. Had the whole front rotating assembly serviced (HB,pulleys,water pump, tensioners, all new belts etc).
Took car to the track today and high pitch buzz/vibration is still there, now very noticeable 80-85mph. I can now rule out anything rotations in front of the engine so question is, what is next? Torque tube tear down? I've checked what I can under the car when on lift etc to no avail.. Ideas welcome!

 

Have you done the checks that several people here have suggested?? Have you sat in the car, not moving, put car in neutral, depress clutch pedal (disengaged) and rev engine at a steady rpm (try 3600), and checked if vibrations are present in this state? If you feel vibrations in that state, you may have an engine balance issue, as your propshaft and wheels are not rotating. If you DO NOT have vibrations at that state, then let out the clutch pedal (engaged) and then DO have vibrations, then you could have an issue with your propshaft, couplings, etc. If you still DO NOT have vibrations with the clutch pedal out, revving at the same rpm, not moving, but then drive the car and have vibrations at some VEHICLE SPEED (like 80 to 85 mph as you have said) then you may have a wheel balance issue.

Trouble shoot in a logical manner that tries to isolate the probable cause of the vibrations, otherwise you will spend a lot of time and money guessing.

It sounds as though you have an aftermarket flywheel/clutch assembly that I would bet any amount of money that it was not match balanced to the stock FW/PP. That is one possibility alone. Balance weights are sometimes installed in the stock clutch assembly and HB to FINE TUNE total engine balance strictly for NVH considerations.

 

I will try and outline below what I have done so far:

Car standing still, clutch in (depressed):
RPM 2300-2800-ish range.
Vibration/buzz is active.

Car standing still, clutch out (released):
RPM 2300-2800-ish range
Vibration/buzz is active.

Car moving, 6th gear:
80-85 mph, droning/buzzing vibration (reminds me of similar symptoms of a u-joint going bad)

Things I have checked so far:
Wheelbearings, 12 o'clock 6 o'clock I can feel no play. I don't feel anything strange while rotating either.

Exhaust mount: checked there is no contact against chassi that causes vibrations.

Front rotating assembly: I was pretty sure this was contributing as I could see a slight wobble to the harmonic balancer prior to replacing but it made no difference. I did replace all rotating assemblies including belts, as it was due for maintenance anyways.


Things left to be considered:
Half shafts, seems like a long shot. But how do you check if suspect?
Torque Tube, I assume only way to check is to tear it down and inspect?
Clutch/flywheel, same thing as above.
Rear diff, how to check? (fluids have been replaced).
Transmission, how to check? (fluids have been replaced).

The tricky thing is that the symptoms are present both standing still and moving, but changes in characteristics as I reach the 80-85 mph zone. I can depress the clutch, and coast in that speed range and still have it drone/vibrate.

 

you very well may have multiple issues contributing to vibrations. However, at a minimum, your test of sitting still, revving engine with gear in neutral and clutch pedal IN suggests an engine assembly balance contribution. You could try an in car balance using washers at PP bolt locations, as you mentioned. That would be free, except for your time.

When you say you experience a different type of buzzing/drone at 80 to 85 mph, it could also be drone from your Borla Stingers. Could be. Plenty of people have complained about droning at "cruising" speeds.

Plenty of people have done the PP bolt hole washer exercise with good results.

 

did you have your HB replaced? If so, do you still have the stock HB?

 

Multiple issues is what I am thinking as well, so will take a look at PP.

The issue at speed has gotten worse and it comes to mind as similar symptoms when a u-joint goes bad and you get that type of feedback through the chassis. The rpm dependent vibration when standing still could be the exhaust for sure, but the issue at speed is definitely something else contributing.

I'll have to get the car on a lift and start digging as this is still mostly speculations.

I wish something would just blow up so it would be obvious what's going on