Scratching My Head WTF is that sound?

Ok, I'm new here and thought somebody has had to have this experience also.

I currently own my 2019 Platinum Tundra. The only modification I have on it is aftermarket rims (+18 offset) with OEM tires. The tires have about 30% life in them remaining. The truck it self just hit 29k miles. Oil changed every 5k miles. Needless to say I baby this truck like crazy.

A few months back I started noticing this humming sound that sounds like a high frequency vibration/humming. Not very loud almost blending in to the sound of the truck. It sounds like it is coming from the driver's side wheel well or under the hood. But it only lasts maybe a 30 seconds when it happens.

I have been trying to identify triggers for the sound and these are the conditions when the truck makes the sound.

1. Cold engine, maybe 3 hours since last drive.
2. In reverse mostly when backing up and moving at a crawl. Sometimes not even moving at all but always in gear.
3. Break pedal depressed but not fully, just enough to crawl backwards or stand still.
4. The noise goes away within 30ish seconds and is intermittent when it happens. (Difficult to hold)
5. If I leave the truck running for 45 seconds after starting before putting it in gear there is no noise.
6. If truck has been driven and is warm. No humming.

I have checked power steering fluid, looks clean and is full. I looked at anything that might not be tight can't seem to find anything wrong.

I usually let the truck sit and warm up a few minutes but on occasion have been in a hurry and started to hear this.

Anyone have a similar issue or have any idea what this is?

 

SAIS system?

 

Would all the models be doing this if it were the SAIS? I pretty sure it has never done this before now. If it were this system what would be actually causing the vibration/humming sound?

Also I googled the SAIS sound and it doesn't sound like it is it. My sound is much deeper, more like a buzzing humming sound. Doesn't sound like air. Sounds like somthing is vibrating at a very high frequency.

 

Has some “fans” or “air pumps” inside of it to dilute the exhaust gas at the tailpipe so it meets emission standards. In auto manufacturer speak, it adds air to the exhaust to “complete the combustion process” or “increase catylist efficiency”. All the Tundras have them. Not saying this is your problem, but they operate differently at startup in a cold engine than they do once it’s warmed up. Just made me think of the conditions you stated and they aren’t super noticeable to most.

 

Wouldn't this create the sound regardless in park as well. The interesting thing is in my case everything sound just fine in park. It's only once I put it in gear and start moving. If I press hard on the break and stop moving it stops. If I press gently on the break to stop moving occasionally I can hold the sound for a few seconds. But that would mean it's my breaks vibrating or somthing. I don't even know if that is possible. I have a gut feeling it is somehow related to the wheels/ breaks or steering. Could a worn out break pad cause such an issue? I believe mine are around 30 to 40 percent? But then again, why would it not do it after 45ish seconds? Totally bizarre

 

Yes, it would make the sound regardless of gear position I would think. Just spit ballin’ from afar. Without being able to sit in it and hear it, by description yours seems to be part of the rotating driveline assembly. Need to get someone else in your truck replicating those conditions so you can listen from outside to pinpoint the source.

 

I will keep trying to investigate, my wife unfortunately hates when I go down a rabbit hole like this so she never helps. But it is driving me a bit crazy. Lol

 

Hmmm, not sure if it totally matches your description of when it happens but have you heard of the ABS self check?

 

Yes, I know it does the ABS self check. That is a quick little jolt when it does this. This issue is definitely not the self check. I'm inspecting under the hood again right now to see if anything is loose. Can't see anything yet.

 

Sounds suspiciously related to AIP as they run for about 35 sec after start only on a cold engine, and if the truck is in park the high idle + mechanical fan drowns them out

 

Ok so I think I figured it out. I was backing out today and heard it make the sound as I was turning the wheel out of the drive way. I caught it mid turn and held it and the sound was intermittent. I suspected power steering again.

I went down to auto zone and got some tools and did a complete flush of the fluid. As I was sucking the old fluid out I was shocked to see how brown it was. I say shocked because doing a dipstick towel test was not noticeable. However once all of it was drained into a jar it was quite filthy. I ran some new ATF through the system as a rinse and filled her back up.

I was shocked at how much easier the steering wheel turned. Almost no effort using one finger. Surly this difference was somthing I grew used to over 4 years. Having changed the fluid was eye opening.

After 29k miles and 4 years, I figure having +18 offset rims puts more strain on the power steering causing the fluid to heat up more and break down quicker. Either that or it was just the time. So far i have not heard the sound and she steers super smoothly.

If you are having strange sounds I would deffinently take a look into your fluid. Especially if you haven't changed it recently. But really suck it out and look at it with a flash light because just using a dipstick and a towel is really deceiving.

Good luck guys.

 

Had an unexplained noise on mine that would usually happen in reverse and it ended up being the mounting tab for the harness that runs along the firewall had broken and was vibrating against it. Put a zip tie on it and no more noise.