Help with Driveline Vibrations

[Surfergeek]

These have been present for a while, and I had just about given up on them, until my mechanic drove my car this week after finishing the maintenance and brake upgrade and commented on it so I feel I need to circle back and address it.

I guess I have just gotten used to them, but how can I diagnose?

I have Cortex Coilovers front and rear (Konis), Cortex Torque Arm, DriveShaftShop Carbon Fiber Driveshaft (with CV Joints), Fays 2 Watts Link (Center hole), TR6060 Swap, and RAM Clutch, BMR adjustable rear control arms (they are in appropriate position)

Clutch: RAM Street Dual Disc Force 9.5 Clutch w/ Flywheel

The vibration consistently creeps in around 80-85mph plus and doesn't really go away, getting a little worse as speeds go up on track. Having not really known anything else since we did the transmission swap / torque arm install, I just kind of assumed this was the way it was, but I guess it's worse than it should be. It doesn't prevent me from getting the car up in the 120s/130s or higher, it's just really present.

The Vibration is present on street tires NT05s / Track Tires NT01s in the same place so I know it's not wheel / tire issues as it's happening on both sets.

The DSS DriveShaft has CV joints so it shouldn't be as sensitive to pinion angle, and that all checks out as it should.

Alignment was done by Custom Alignment and is spot on.

Could it be clutch related? Should I be looking at different clutch? (I am at 610WHP right now, 522TQ)

Do I need to shim the torque arm or adjust the torque arm in some way, pinion angles check out, DSS with CV joints is supposed to eliminate sensitivity to that anyways.

Any input / suggestions for places I can take it to have it checked out in the bay area? Is this a job for Cortex?

This is a tough one to diagnose as you can't exactly bring it up to 120+ on the street in a controlled environment. Open to any input, this is well out of my acquired knowledge so far and just looking to learn as I get it diagnosed.

 

[Surfergeek]

So did some troubleshooting this weekend, I think we can rule out the clutch?

Tried, 4th Gear, 5th Gear, 6th Gear, vibrations still start creeping in around 80mph in all gears.

Tried depressing clutch in each gear ... no change

Tried putting it into Neutral in each gear ... no change

 

[302BOB]

Surfergeek, I feel your anguish! Your problem is surely in the drive train..has the drive shaft been ruled out as a cause?

 

[Champale]

Judging by your symptoms, I think 302BOB is on the right track. You might want to check in with longtime member FlyboyGSXR about his trevails with his DSS shaft. There have been plenty of problems documented with that brand on this forum and many others.

 

[Norm Peterson]

Agreed. Being speed-sensitive rather than engine rpm-sensitive puts it on the output side of the transmission (which would include the transmission output shaft and its bearings).


Norm

 

[TMSBOSS]

Do you still have the factory two piece shaft? Can you swap it in for a test?

 

[Surfergeek]

Do you still have the factory two piece shaft? Can you swap it in for a test?

I can’t because we did the TR6060 swap I never have had a factory shaft that fits with this transmission.


Sent from my iPhone using Tapatalk

 

[Nvrfinished]

Yes, check your driveshaft. You have the same symptoms I had initially. I have an S550 with a DSS CF driveshaft and had issues when I first installed it. I'm not familiar with the S197's, but the S550 pinion angle and tail shaft angles are less than ideal for a 1-piece driveshaft and will cause vibration to rear its ugly head. People have had these problems with various brands of 1-piece driveshafts for the S550 in both aluminum and CF.

Start with clocking the driveshaft at the rear first. I spoke with DSS about this and they recommend 90 degree changes (or close depending on bolt pattern). If that doesn't solve the issue, return the rear to the position where vibration was noted to be the least and then clock the front.

Clocking the rear got better for me, but I finally solved the issue when I clocked the front and lowered the transmission mount about 3/8". It now runs smooth as silk. Give DSS a call and they will walk you through the recommend procedure.

 

[Fat Boss]

Check your pinion bearing too.

 

[Senna1]

Sounds exactly like what my '13GT does, stock. Only mine starts at ~65 mph.

Dealer replaced my pinion bearing (twice, after not properly setting the pre-load 1st time), and I'm highly suspicious they didn't clock the DS right putting everything back together. Other than that, I plan to check the runout on the rear axles/wheels with the car in gear on stands, as well as the condition of the UCA diff bushing.

After that, I'm out of ideas, but it sure is low-grade maddening driving down the highway this way, so I feel your pain. And there's no way it gets anywhere near a track until this is addressed, or confirmed to be a non-issue.

 

[DocB]

How much are you lower than stock ride height and what is your pinion angle?

 

[Surfergeek]

How much are you lower than stock ride height and what is your pinion angle?

Pinion Angle is at -2, lowered about 1 inch.

Won’t be able to address some of the other items for a couple of weeks as I just won’t have time but thank you everyone for the input. I think clocking the driveshaft is the next step we need to take.


Sent from my iPhone using Tapatalk

 

[Surfergeek]

Spent some time with the driveshaft this week, didn't have all the time we could use, but made some progress.

The driveshaft checks out okay, we shimmed the transmission end of the Cortex Torque arm, and it made a difference with the vibration. It now starts coming on much later, but won't be able to really check it out until the track this weekend.

I am confident we will get it figured out, may have to create some plates to shim the torque arm front or rear to adjust wheelbase / driveline angle and get rid of the vibration entirely.