Whistle whine howl sound in rear.

I posted this on an A/C whining thread but I don’t believe that is my issue. My 22 has made this noise for about a year. I started noticing this after installing a Leer cap so I thought it was wind between the cab and cap. It has worsened lately so I took it to the dealer. They think it is related to the rear differential. I only hear this when lightly accelerating (feathering) between 50-60. As soon as I let off the accelerator it stops. I have seen several posts about this and I also heard this same exact sound in a 21 4Runner I recently rented. Seeing how common this is, I’m surprised it hasn’t been narrowed down to the exact culprit. Lots of theories but they seem to vary between AC, Diff and wind. Maybe I missed the thread where it was solved but I would like to have the best info when I return to the dealership. I’d rather not have them rebuild my diff or open my dashboard if it’s not going to fix the issue. Any solid info would be greatly appreciated.

 

Eliminating the AC is easy if you just follow the reproduction steps in the TSB noted in the other thread:

Code:

1. With the vehicle engine running in Park and the parking brake firmly applied, turn ON the air
conditioning and set the temperature to low. Slowly bring the engine speed to 3,000 RPM and
hold this RPM until the compressor begins to cycle ON and OFF.
Is there a 1 – 3-second whistle noise heard from the air conditioning system each time the
compressor cycles ON/OFF during hot ambient temperatures?
 YES — Continue to step 2.
 NO — This bulletin does NOT apply.

Other TSBs that might be of interest although they don't seem to cover 2022.
https://static.nhtsa.gov/odi/tsbs/2021/MC-10198138-9999.pdf
https://static.nhtsa.gov/odi/tsbs/2018/MC-10149973-9999.pdf

 

Thanks! Tech Tip T-TT-0651-21 sounds exactly like my issue. Actually both do. I will show this to the dealership.

 

Maybe your cause is from reading too many of these complaints on tw. Now you believe you've got them to.

 

Nope… The noise is definitely there.

 

Vocal critical minority, but if there's an abundance of threads and discussion about an issue, chances are there's an issue.

I have a 2020 and get it from the rear diff steady at 67mph. Problem is...that's where I hit my cruise all the time mine's not that bad, I didn't notice it until about 40k, and it's nothing out of the (relative) ordinary. I have a roof rack and wind noise anyway, not a big deal.

But it's there, and there for many other people. Something about resonant frequencies coming from the diff. I don't care enough to spend time on it, got bigger fish to spend time on.

 

If I hit a bunch of cross winds going over 45 mph, I get some crazy wind noise only when I have the tonneau cover installed, otherwise I'll get a different wind noise at similar speeds if I remove the chin spoiler. That said the truck is very quiet the rest of the time.

 

rear Differential gear noise , not uncommon i have had two replace under warranty & last one started the same noise after 6000 - 7000 miles but truck is out of warranty