Whole car vibration @ 135+mph HELP!

[Vettel-ish]

UPDATE!

After the awesome team over @Middleton Motorsports took care of the car in spring. Did get some nice upgrades. More to come on that. They did determine that the driveshaft was bad. Ordered a new one and installed it before the first track day. Road America, here we go!

Car ran really good up to about 120. At that speed its hard to tell if its wind/aero or driveline. However @ 135+ the vibration is still there and comes on strong. When I say strong I mean you can see out of the rear view mirror the car is vibrating so bad.

Next steps are look at the angle attaching the driveshaft and engine mounts.

Anymore thoughts on this?

 

[blacksheep-1]

I doubt it's the driveshaft angle, I think it would have to be pretty bad to cause a vibration. Did you pop it out of gear when it started to vibrate?
Maybe it's time to find a chassis dyno.

 

[Vettel-ish]

I doubt it's the driveshaft angle, I think it would have to be pretty bad to cause a vibration. Did you pop it out of gear when it started to vibrate?
Maybe it's time to find a chassis dyno.

That is a great idea. They are going to do something and yes need to try and at road America next.

Would it hurt anything by doing that? At that speed don't want anything to go wrong lol

Second question. What is wrong if I do and it goes away?

 

[Bill Pemberton]

I realize you have likely checked this, but I had a horrible vibration at around 130 mph and I decided to check on the simplest thing by checking the tires to see if one was out of balance. We had check hubs and other areas and shockingly it was exactly that , with one wheel had lost all its weights and it was way, way off. Good luck and sorry to hear you are having issues.

 

[blacksheep-1]

That is a great idea. They are going to do something and yes need to try and at road America next.

Would it hurt anything by doing that? At that speed don't want anything to go wrong lol

Second question. What is wrong if I do and it goes away?

Well, let's think about this logically, because sooner or later, everything mechanical has to respond to reason.
1. if you've run the car up to 7 or 8K in 1st through 4th gears, and there was no vibration, that means there is probably nothing wrong with the engine or the input shaft and gear clusters 1 to 4.
2. if you are running 135 and you pop it out of gear, and the vibration stays, that would mean clusters 5 and 6 are probably OK, and the vibration is farther back.
3, You've changed out the drivesahft, so let's say that is about a 10% chance of being the problem, which leaves everything else, the diff, let's face it, they are pretty bulletproof, so let's assign that a 10%, So you might have a bent axle... say 25% chance depending on what you've run over or into,...a bent wheel assembly, again about 25% , so then we have wheel balance I'm saying 40% chance of being the problem.
There's an out side chance it could be aero, were the window sup when the vibration occurred? if not roll them up and see what happens. Try and find a photog to take some pics on the long straight and see what the car is doing, are the diffusers all bent down pulling the front fascia down? there could be a bunch of stuff there. At Homestead we had exactly that happen (fascia) on a car, no one believed me until I was able to get a pic on the big end and show them., it was amazing what it looked like, air was actually entering the hood through the front of it. They thought they had some other issue, just like you,
So, if it's not aero, I'm going with a bent wheel or axle, when you have the wheels re balanced hang around and see them spin them up, you can place a straight edge on the balancer, against the wheel and see movement.. don't be surprised, you will see a LOT of movement, but anything over 1/4 inch should be suspect, After that, look at the rear axle flanges and see what happens when someone rotates the diff. It's a limited slip so both rear wheels will have to be in the air. If a wheel is bent, it could have bent the axle as well.

 

[Vettel-ish]

Well, let's think about this logically, because sooner or later, everything mechanical has to respond to reason.
1. if you've run the car up to 7 or 8K in 1st through 4th gears, and there was no vibration, that means there is probably nothing wrong with the engine or the input shaft and gear clusters 1 to 4.
2. if you are running 135 and you pop it out of gear, and the vibration stays, that would mean clusters 5 and 6 are probably OK, and the vibration is farther back.
3, You've changed out the drivesahft, so let's say that is about a 10% chance of being the problem, which leaves everything else, the diff, let's face it, they are pretty bulletproof, so let's assign that a 10%, So you might have a bent axle... say 25% chance depending on what you've run over or into,...a bent wheel assembly, again about 25% , so then we have wheel balance I'm saying 40% chance of being the problem.
There's an out side chance it could be aero, were the window sup when the vibration occurred? if not roll them up and see what happens. Try and find a photog to take some pics on the long straight and see what the car is doing, are the diffusers all bent down pulling the front fascia down? there could be a bunch of stuff there. At Homestead we had exactly that happen (fascia) on a car, no one believed me until I was able to get a pic on the big end and show them., it was amazing what it looked like, air was actually entering the hood through the front of it. They thought they had some other issue, just like you,
So, if it's not aero, I'm going with a bent wheel or axle, when you have the wheels re balanced hang around and see them spin them up, you can place a straight edge on the balancer, against the wheel and see movement.. don't be surprised, you will see a LOT of movement, but anything over 1/4 inch should be suspect, After that, look at the rear axle flanges and see what happens when someone rotates the diff. It's a limited slip so both rear wheels will have to be in the air. If a wheel is bent, it could have bent the axle as well.

Sent that to my shop. Thank you!

 

[xr7]

Do you feel the vibration building with your hand on the shift lever? Swap a different set of tires on it, possible ply separation, a tire with ply separation can balance just fine. Bad u-joint. Also check run out at driveshaft attachment points. I agree with black sheep, if you can get video of car from both sides, aero can do some bad stuff if it flutters a splitter, wing or spoiler.

 

[Mad Hatter]

Good idea to check the engine mounts, My poly bushings got oil on them and turned into mush.. car was fine until +130 when it started to vibrate like crazy.

 

[Vettel-ish]

The shop is checking engine mounts.

I have had 4 sets of slicks and a set of rain / cold tires on 2 sets of apex wheels. All did it sadly.

 

[blacksheep-1]

The shop is checking engine mounts.

I have had 4 sets of slicks and a set of rain / cold tires on 2 sets of apex wheels. All did it sadly.

Ok, so we're down to bent axle flanges, and aero...

 

[Vettel-ish]

Thanks for the help guys. Updates coming as soon as they done.

Road america May 6th and 7th!

 

[Boone]

I've had a high speed (110+) vibration that turned out to be a drive shaft. Vibration was much more pronounced when lifting off the throttle. The drive shaft checked within spec, but I paid them to balance it from scratch. Vibration went away. Also, my T3650 will shake violently in 5th (top gear overdrive for me). It's one of the reasons I swapped from 4.10 to 3.55. I'm not sure what will happen at big tracks where I need to do 160+. Tuning in to see what the magic bullet is for you.

 

[Vettel-ish]

Small update. Pinion angle was north of 4 degrees. It has now been set to just under 1 degree. Could not tell you what this means but wanted to share

 

[Vettel-ish]

Another update..

Sadly no change after the driveshaft or shims.

I was able to put the car into neutral at 140 during the vibration.....nothing changed. Vibrate was still as powerful. What does that mean now?

 

[xr7]

Another update..

Sadly no change after the driveshaft or shims.

I was able to put the car into neutral at 140 during the vibration.....nothing changed. Vibrate was still as powerful. What does that mean now?

There is a device out there called a vibrating reed tachometer. It can be handy for finding vibration issues. You would mount it in the car, have a camera focused on it and go out on the track and duplicate the vibration. The reed tach will give you the frequency of the vibration and then you start figuring out what's rotating at that frequency. This thing isn't cheap, perhaps there is some electronic device that could sub for this.
I'd be checking runout on wheels and hubs, any excessive axle moment, dump the diff lube and trans lube and exam for debris. A bearing going out maybe? Unfortunately popping it into neutral didn't eliminate any suspects.

https://www.coleparmer.com/p/vibrating-reed-tachometers/58352

 

[Mad Hatter]

Which UCA do you have?? I had a BMR spherical that i had to remove a while back after it got a little worn. Went back to stock.

 

[Techapma]

I second the suggestion that you need to measure the vibration in order to be able to figure this out. I have used an app on my iPhone to collect vibration data with marginal Success. You’re best off with something more suited for the job, such as an accelerometer w/data acquisition unit. Pico automotive makes a NVH kit to go along with their oscilloscope. What makes this kit appealing is that the software allows you to enter all of the specs related to your drivetrain, and it will help pinpoint the suspect component. If you can find someone that has this type of equipment, they should be able to narrow down your problem within a very short period of time.

In reading your chronology, it appears you changed the drive shaft before having the pinion angle corrected. If that is accurate, operating the car at high speed with a jacked up pinion angle could have damaged the new driveshaft.
I don’t know what the driveline specs are supposed to be for your car, but at 7,000 + RPM driveline speed there is very little margin for error.

a bad vibration at those speeds isn’t something to take lightly.

 

[blacksheep-1]

Another update..

Sadly no change after the driveshaft or shims.

I was able to put the car into neutral at 140 during the vibration.....nothing changed. Vibrate was still as powerful. What does that mean now?

the vibration is not engine or flywheel related, and you can most likely remove the trans from that list as well.. Drive shaft and the rest of the rotating running gear is still in play. Did ypu check the wheels for runout on the balancer?

 

[Short circuit]

I had a high speed vibration around 120+ due to badly warped front rotors....fyi