Vibration Help

[davesz4mc]

ok time to let some outside opinions in as this is driving me crazy!

Vibration on my Z4 M Coupe S54 between 2000-2500 RPM.

Parts checked/changed: Problem has exsisted before and after these changes/checks. 90,000 miles on car.

Coils - new
Plugs - new
All oils changed - new
Motor mounts - new stock updated part number
Tranny mounts - new Black UUC
Mount bracket bolts - new grade 10.8
Valve lash done - all in spec
Vanos tabs good - checked during valve lash
New clutch kit - UUC LW

No noises or knocks at anytime during operation, strong performance and vibration gets remakable better at 3k rpm and starts to come back at ~3500+RPM depending on load. Butter smooth at 70 MPH but rough at 65 or 80 MPH, butter smooth at all speeds in nuetral clutch out.

No active or stored trouble codes to date.

Headers, custom exhaust and Evolve tune all installed and pre-exsisting to condition.

Any ideas I am pulling what little hair I have left out.

[XMetal]

Did you check the vanos intake hub bolts?

[davesz4mc]

I did not pull the vanos and cam gear to put a wrench on them but an inspection from the back side they all looked equal.

[Pheonix]

I would look into the Tranny Mount because you said "butter smooth at all speeds in nuetral clutch out"

[davesz4mc]

Sorry, stopped clutch in it vibrates 2-2.5k RPM as well. Tranny mounts are new as posted above.

[seank]

Drive shaft or drive shaft support bearing. Those take abuse on the track. The bearing support could also have play in it. Also the flex disc or guibo probably needs replacing at that mileage.

[davesz4mc]

should of thought of everything to mention up front lol

New Guibo, CSB and rear CV joint on the drive shaft. Expensive to keep replacing stuff.

Keep the ideas coming it is appreciated.

[Finnegan]

So it vibrates at those RPM ranges you noted in any gear?

Since you've ruled out the engine itself, it's somewhere in the drivetrain. The driveshaft bearing Sean noted seems to be the only other thing besides the diff itself I can think of.

[davesz4mc]

I think it ruled out the drive train since it does it stopped with the clutch in, it does it in any gear at any speed at that RPM range get worse with load.

Have seriously considered a new car at this point, Put an eye on the vibration dampner and it "looked" good no missing peices or visable cracks.

[davesz4mc]

Last thing left is an idler pully or the like maybe? Seems like ALOT of vibration for just a pully though. The whole car shakes, rattles chage in the ashtry. Not like it is coming apart though.

[seank]

Originally Posted by davesz4mc

I think it ruled out the drive train since it does it stopped with the clutch in, it does it in any gear at any speed at that RPM range get worse with load.

Have seriously considered a new car at this point, Put an eye on the vibration dampner and it "looked" good no missing peices or visable cracks.

I am not following. So, if you sit in your driveway and rev to that RPM (clutch in of course), it starts shaking?

If you put in the clutch at 4000rpm and wait till it drops to 2500 RPM's.......it vibrates.

Just clarifiying because if you put the clutch in at 2500 rpm's, it will drop past the vibrating point quickly so you could assume it isn't the issue.

Also, it only takes a second to check the guibo and drive shaft for play.

[davesz4mc]

Only at 2500 RPM with the throttle pressed, clutch in or out, at any speed in any gear worse in gear under load. Smooth in comparison at 3000 RPM. In 6th gear if the RPM is 2000 or under or ~2700 or over it is smooth but at 2500 it vibrates. you can speed up slow down or go to a lower gear that raises the RPM to stop it. However, the same is true for gears 1-6 at the speed of that gear that the car is turning 2500 RPM.

Seems kinda pulsating as well.

It vibrates stopped clutch in holding RPM steady at 2500 or as above.

Guibo is new as well as the CSB and rear CV joint. The U-Joint seemed tight with no play when I changed the rear CV joint. Rear joint was changed last and everything rechecked at that time. The any speed thing as well as the vibration when stopped makes me think it is not drive train related. However, it is very mild stopped in nuetral holding 2500 RPM than it is moving under load, but since it is ever gear at that RPM range and not speed dependant I am puzzeled at what it could be in the drive train.

[gmd2003]

What kind of exhaust do you have ?

[seank]

This is what my mechanic said after I forwarded him the link to this post:

"Broken engine fan blade if it has a mechanical engine cooling fan (which you don't have) or bad crank damper since it does it stopped and just revving the engine. And the question we always ask, what was changed or happened just before the vibration started.

Just trying to help.

[gmd2003]

Im asking because I had severe vibration from my RE diablos at those RPM's that have almost been eliminated by replacing my Exhaust hangers which were shot (Car is a 2006) with the DKF ones. I'm talking I set off every alarm in my parking deck at work bad lol
George

[davesz4mc]

Interesting will have to scope that out, my exhaust is cutom made. I have no mufflers after the axel just one aero turbine in the center of the car. There are threads on it.

Noticed the change after installing Red Poly engine mounts. I noticed the Mount brakets had loose bolts so those were retourqued when the mounts were installed. With the red poly I was unhappy with what I believed to be the added NVH so I re-installed the stock mounts and replaced the mount bracket bolts with 10.9 hardware while I was at it. However, being back to stock the way it was before it still had the same vibration with the only change at that point being no loose bracket bolts. Txz4 lives close by though and I do not feel any of those vibrations in his car. It was never like that before, I will look to see if tightining the brackets did something with the exhaust as the engine placement may of changed after those bolts were retorqued.

I know there is no "rub" on the exhaust because we looked for that but maybe it shimmies without really touching anything causing the vibration?

I do not know though, the mount brackets were not sagging or anything just 1 loose bolt on each side.