Yes, HB replaced. I do not have stock HB.

 

I have Stainless Works Headers and the complete cat back system. I found the bracket that bolts both collector to the bell housing to be cracked on my set up.

Point taken is,,, Make sure that you dont have a simple exhaust system isue making the niose. My crack was difficult to find as when the system was cold, the crack was difficult to see. once it heated up, I could see it a lot better.

 

Need also to consider what gear trans is in. For example if the car has 750rpm idle and does 70mph@2500 then:

 

I'm having similar issues in my c5 z06 after 4 months of an a&a Kit on it. Previous owner road raced the car so constant high rpms and throttle, thus shocking the drivetrain. I believe from what ive researched that this is a torque tube rebuild and from what U r describing is similar Id guess this is your issue as well.

I recently spoke with rpm transmissions and I'm going to order up the stock rubber couplers and the new bearings. Asked about the polyurethane ones and was told if I'm worried about vibrations now you're not gonna like the polyurethane ones. Much to my dismay they told me the polyurethane ones don't last as long as the rubber ones either. I guess from what I gather they may be stronger thus giving a rougher ride but over time they wear just as fast if not faster than the rubber ones. Just my $.02... When In doubt call the experts!

 

This is with the car in NEUTRAL. Car is not moving. Car in neutral, clutch pedal depressed means nothing else is spinning but the engine/FW/Clutch assy. Propshaft inside the torque tube is not spinning, thus not contributing. Nothing inside the transmission is contributing. For this "test" only. There may be other contributors as mentioned, but for this test, only the engine/FW/clutch assembly is contributing to vibrations. (of course an exhaust system component that is touching somewhere could contribute also).

 

how does the propshaft inside the torque tube contribute when the car is in neutral, not moving, and the clutch pedal is depressed (clutch disengaged)??

 

Now that I've read your entire post,,, I would have to say that you most likely have a Fly Wheel out of balance condition...

Like you stated previously, its not difficult to systematically add washers to the pressure plate bolts and see if the vibrations increase or decrease in each bolt quadrant and work from there.

That would be where I would go next if it were my car.

NOTE! Don't forget to calculate in a LONGER pressure plate fastener into your washer stack once you find the correct offset weight. The OEM pressure plate fasteners do not have that much thread protrusion in the OEM configuration to be adding washers under them!

Please let us know how it turns out and PICTURES !


Bill

 

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the Headers/exhaust!!! Just one bolt of exhaust system touching the chassis or frame, can cause the exact 'vibration' as you describe. Ask me how I know???

Upon visual exam, you'll probably find it. Or, look for shiny marks on chassis, where under torque; the headers/exhaust system is 'torquing over', shifting just a little as motor torques and rears up, and touches the frame. But, at rest or idle, without torque shift; it does not touch.

Sounds exactly like what I had, and we found the 'shiny' scraping marks where a longer than stock 'bolt' on new installed exhaust was able to reach and touch the frame, under load. At times, made the whole car vibrate, other times, just the steering wheel/dash.

Found the culprit bolt, replaced it with one 'not' too long; and problem gone.....
Hope your fix is simple, like that. Just get the car up, so you can really inspect it well.

good luck,
Don

 

Thanks for the replies. I will get the car on the lift this weekend and do another inspection, if nothing obvious is found I'll start tearing into it.

 

Please tell you you figured this out. I have the same vibration. doesn’t matter if I'm moving or parked, clutch in or out.
I have done a lot trying to fix it.
1. put a entirely new RST clutch/flywheel assembly on.
2. new slave
3. new Tick adjustable master
4. all new SKF bearings and new OE couplers in torque tube
5. Trans diff brace and billet rear diff support
6. fixed exhaust mount for x-pipe that was missing
All this and the vibration is still exactly the same as it was when i started.
harmonic balancer looks straight even when being revved.
really want to get this solved so I can enjoy my car

 

I would rule out motor mounts and trans mount,
If the trans mount is stiffer than the motor mount it will fail to dampen natural frequency of the engine
Unlikely? but its on the list of things to check as you move along and I don't see much attention where all of the contact is made from the heaviest parts of the drivetrain to chassis

 

I've had the same issue. Please tell me you found a fix.

 

Turned out to be a bad stock motor mount. The factory liquid filled motor mounts will give you signs when they start to go such as vibration or an out of place “oil leak” which is actually the hydraulic fluid leaking out of the motor mount.
Hope this helps.