Groan Noise at 73MPH and Slight Vibration in Steering Wheel - High T1 from RF

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Groan Noise at 73MPH and Slight Vibration in Steering Wheel - High T1 from RF

Post by ToyotaTech »

Hello Forum,
Been using the Pico NVH for about 3 years now, but having a tough time diagnosing a groan noise at 73 MPH on light acceleration. Vehicle is a 2024 Tundra with 1,100 miles. No aftermarket accessories or tires/wheels.
When letting off throttle, groan is reduced significantly (but still felt). There is also a slight vibration felt in the steering wheel. I've also found that on take offs at slow speeds, I can feel the same vibration in the steering wheel.
Hooked up the Pico and found high T1 vibration. When hooking up accelerometers to the right and left front, found high T1 from right front.
Rear differential was replaced early on prior to NVH equipment being utilized.
Since finding the high T1, both front axles were swapped form known good, with no change. Front right spindle (knuckle,bearing,rotor) were swapped and no change. All 4 wheels and tires swapped from known good, no change.
Going back to my dealer tomorrow to start from scratch and hook up accelerometers to all 4 corners, but wanted to try using this forum to see if there are any suggestions or advice.
Suspect possible front differential, but want to be sure I'm not missing something. Any advise would be greatly appreciated for a newcomer to this forum.
Thank you in advance!
Test Drive 4 - LF and RF Wheel.pddata
(885.76 KiB) Downloaded 24 times

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Re: Groan Noise at 73MPH and Slight Vibration in Steering Wheel - High T1 from RF

Post by wmarlexingtonsc »

Hello Sir,
Please take my advice with a grain of salt. I am no expert on NVH or the Pico kit. However, I want to be helpful. I am sure that Steve Smith will eventually chime in with advice that you can trust. In the meantime though, I have been reading through all the posts on this NVH forum and have a couple ideas that you can try.

The first thing I want to say is what a blessing it is for you to work in a dealership and be able to have so many known good parts at your disposal for this job. All my life I have worked in an independent garage where we service pretty much anything. This means the lot is always full of a near infinite variety of makes/models/years, etc., which makes it hard to easily find known good parts to swap around. I have always thought this must be a great advantage of working at a dealership: a known good is normally just a few bays down. In an older post I made on T1 vibrations, Steve Smith wagered that MOST T1 vibrations are the result of tires or wheels. You have eliminated so much headache by being able to swap known good wheels and tires to the vehicle. We can infer then that the source of the T1 vibration is not wheels or tires or a road force issue. This leaves possibly issues with runout at the hub, but I don't think these would explain your groaning noise under throttle.

That being said, just to clarify about your original post, you mentioned a slight vibration that is felt in the steering wheel. Does that only occur when letting off the throttle, at the point when the groan is reduced, or is the vibration occurring at the moment when you hear the groan?

Does side to side movement make any difference at the speeds where the groan occurs? E.g., an aggressive lane change on the interstate to the right or left when no-one is around you?

From your original message, it seems like the groan (noise) is more long-lasting and pronounced than the vibration. Is that a fair assessment? If so, perhaps you would have better luck isolating the largest source of SOUND, rather than chasing the vibration? Hopefully, once you find the sound, you will find the vibration also.

Have you tried using the accelerometers as microphones? Apparently, the microphone with the NVH kit is very difficult to get good information off of when used outside the passenger compartment. However, you can export the raw data from your accelerometers into an audio format that you can play back and analyze. See the post: topic21639.html?&p=98097&hilit=new+nvh+ ... 019#p98097 . Look in Steve's first post under "improved export options." If you can place the accelerometers at different places where you think the sound may be originating (.e.g., each hub, front diff, etc.) , then obtain a capture and mark the span of time where the groan is at its worst, you can then export each individual channel to a .wav file and listen to each one with noise cancelling headphones to figure out where the greatest amplitude of the groan is originating. This may perhaps be a way to at least prove the groan is coming from the front diff.

With all the parts that you have already swapped, along with the nature of the noise and vibration as load related/under acceleration, it seems like a fair conclusion to say that something may be going on in the front diff., but I understand the drive to prove this out conclusively is what keeps you second guessing. Is it possible to run the vehicle without the front cv axles and without the front driveshaft? I am guessing not, but it would be nice to see if all the symptoms go away with the front diff completely out of the equation.

I hope you can find something helpful in this message, but perhaps someone with more knowledge will soon chime in.

Good luck!

Steve Smith
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Re: Groan Noise at 73MPH and Slight Vibration in Steering Wheel - High T1 from RF

Post by Steve Smith »

Hello and thank you for the posts and to Josh for following up. (Sorry for my late reply)

For me, this is great to see, Technicians helping and supporting Technicians given it’s NVH which is a challenging topic, but one of the least intrusive tests you can carry out that potentiality yields the greatest return

Going on your initial complaint “A groan you can feel” suggests we are looking for an offending frequency or, frequencies in the realm of 20 to 200 Hz as this is the area where we as humans, we differ in our sensitivity to both noise and vibration

For example:
0 – 20 Hz we all “feel” this vibration
20 – 200 Hz, some may feel, others hear and some both (feel and hear)
200 Hz – 20,000 Hz we all “hear
Please allow for tolerances on the above

The following video will help here

Just looking at your set up, it suggests we have 4 sensors mounted to the front of the vehicle but there is little response from Channels B & D unlike A & C (See Time Domain view below)
Could I ask, did you have 2 accelerometers, one mounted vertically to each hub with the screw thread facing forward?

Did you then have the vertical (Y axis) and Fore/Aft (X axis) outputs from 2 interfaces connected to 4 – channels of the scope? (Just trying to visualize the set-up)

There can be no doubt at 73 mph channel C (RF Vertical) has a high T1 first order tyre/wheel vibration. i.e. something rotating at the same speed/frequency of the road wheel and tyre is creating 1 disturbance for every revolution.
As Josh mentioned, I have stuck my neck out and also supported many cases where T1 faults boil down to wheel/tyre

Please allow me to play devil’s advocate here and ask we try a simple technique of over-inflating the tyres and road-testing again (even though we have changed wheels and tyres)

Overinflating will help the tyres “pop out” if they are soft and misshaped

For a tyre with excessive Radial Force Variation (RFV) increasing the tyre pressure will increase the vibration levels, conversely, decreasing the tyre pressure (with excessive RFV) will improve the condition.

The following case study is worthy of a read and follows a similar journey diagnosing T1

Tyre rolling circumference would be worth considering too, as given this is a 4WD drive vehicle, any anomalies here has the potential to “wind tight” our differential (Thinking about "groan")

I think it would be worth adding a microphone in the cabin and see if we can capture the “groan frequencies” and correlate them to offending frequencies detected by the accelerometers.

If the Mic captures the groan, but the offending frequency is lost in the ambient cabin noise (i.e. The “noise floor”) this is not a problem, we will still have a reference during playback in which to correlate offending frequencies captured by the accelerometer

Please be aware, we as humans are awesome at sub-consciously filtering out background noise in order to focus on offending noises, microphones and recording equipment not so; don’t be surprised (or disappointed) if you cannot hear the groan during playback

Try to keep the cabin as silent as possible (turn off air vents etc.)

The following forum post discusses microphone placement which has a dramatic effect on your results topic23382.html

If we are happy our T1 and groan are one and the same, we can use the accelerometers as listening devices and configure them in the software as microphones.

This is a cheat but will allow playback of each accelerometer within the software without having to export to .wav and listen back in a 3rd party media player, or import back into NVH

More about importing audio here post93381.html#p93381

Given you mentioned the groan does improve when you ease off the gas suggests this could be load or even tooth mesh related as differentials are notorious for generating differing noise levels on “Drive, Over-run or during Cruise” conditions

The low speed “take-off” vibration is very interesting as this is unlikely to be T1 from rest (I hope I have interpreted that correctly)

Once again, coming back to Josh’s suggestion of decoupling the front differential in some fashion would be a worthy step

Returning to your NVH capture "Test Drive 4 - LF and RF Wheel" I have exported the captured data and listened to them in a Media player and cannot hear a groan (See below)
Test Drive 4 - LF and RF Wheel 326 to 369 sec_A.wav
Channel A
(1.68 MiB) Downloaded 13 times
Test Drive 4 - LF and RF Wheel 326 to 369 sec_B.wav
Channel B
(1.68 MiB) Downloaded 12 times
Test Drive 4 - LF and RF Wheel 326 to 369 sec_C.wav
Channel C
(1.68 MiB) Downloaded 11 times
Test Drive 4 - LF and RF Wheel 326 to 369 sec_D.wav
Channel D
(1.68 MiB) Downloaded 12 times
There is however a higher pitched continual noise on channels A & B (may or may not be relevant) with very little on C & D (Food for thought)

I hope this helps, take care......Steve

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