Hello everyone,

I am a relatively new owner picking up my first 2014 M7 Z51 in June 2022. I have been researching my issue for the past few months and have found no relatable information on what I am experiencing and I would like to see if anyone has seen this before/possibly knows the root cause.

The car has an intense/violent vibration when accelerating at freeway speeds over 60+ mph. Here is a list of symptoms:
Vibration is consistent between drives and is not intermittent.
Vibration is felt most from of the seat, center console, and shifter.
Vibration intensifies/increases as the speed/engine load increases.
Vibration resonates most at about 1500-1800 RPM
Vibration occurs at any gear at 60+ mph
Vibration even more noticeable on inclined freeways (greater engine load)
Vibration disappears when clutch is engaged or shifter put into neutral
No vibration is apparent when throttle is blipped while in neutral
The car idles smoothly with no unordinary vibration while stopped or coasting in neutral.
Vibration continues when put back into gear from neutral at freeway speeds.
The brakes have been tested and no vibration added by them.

Thank you if you read this far. From what I understand, the symptoms rule out the engine and its accessories as revving the car while in neutral has no effect. The tires are new Pilot SuperSports with a street alignment done a month ago. Could this be the torque tube causing me this grief? If so, then how come the vibration only appears at freeway speeds?

Let me know your thoughts. I plan on taking it to the dealer shortly.

 

Sounds a lot like a torque tube issue, my has gone out twice with different symptoms. Couplings in torque tube are plastic. Next time it happens I intend on either longer drive line or aluminum couplings. Good luck to you.

 

Welcome to the Forum !!...first thing you shouldn't be taking your car to a dealership for diagnostics...they are clueless !!...ask them if they will be using their Picoscope to diagnose this...the Pico is a computer based labscope (below) and GM dealerships use it for NVH (noise, vibration, harshness)...if they won't be using it go elsewhere or they will just be shotgunning parts which will be expensive for you !!

 

Thanks Diag and murder. I will inquire about the Picoscope and also begin looking into local shops that have dealt with these torque tubes before. Is there anything further I can do to confirm that it is a torque tube problem before taking it to a professional? I have learned my lesson on "shotgunning parts' when I was younger haha.

 

"Normally" if it were a torque tube issue with bad bushings and a bad vibration it can set a P0300 random misfire DTC which there is a TSB of which a part is contained below...the TSB says the affected model years are 2001-2013 but your 14 may be included.




Recommendation/Instructions:

Follow the instructions listed in this PI if SI misfire diagnostics does not isolate the root cause.

Before engine disassembly the torque tube coupling should be inspected for damage.

Remove the inspection cover from the rear torque converter cover and from the engine bell housing cover.

Rotate the engine to access the torque converter bolt, put a wrench on the bolt, move it back and forth watching for movement at the flywheel (should be virtually none).

It has been reported to have up to 4 inches of travel without moving the flywheel on failed couplings.

 

I took the car to the American Heritage Performance in Southern California to diagnose the vibration problem. The shop owner Kohle drove my C7 and told it was most definitely the torque tube causing this vibration and that he could rebuild the unit. Here are some photos of the tube after it was removed from underneath the car. I will also include a link to a youtube video showing the play inside the torque tube: . While everything was out, I inspected the clutch, which looked great for 50k miles or was recently replaced. They rebuilt the tube with 2 new TT bearings, 1 new pilot bearing, and 2 couplers which came out to about $3700. I drove home feeling great but still noticed the vibration, only much more muffled. I climbed underneath the car and spent some time digging around only to find my driver's rear CV axle boot was loose and grease has been spraying everywhere. I got the CV axle replaced, diff fluid changed, and both of the axle nuts torqued (just for good measure) for $1k. After all that, the vibration is now gone and my C7 cruises on the highway buttery smooth.

Overall, I am glad I had the torque tube checked and rebuilt because I would be paying for way more in damages if I waited any longer. I hope the community finds this data useful.