3rd Gen Poll: Rear End Noise howling when feathering throttle

Yeah you must have had a different issue as your situation seems to be the inverse of what everyone else is having. Usually the truck is silent for 500-2000 miles then the howl develops and gets worse over time. Mine peaked at around 3000 miles and has since been about the same... now at 5300 miles.

 

I'm not sure, but check this out (bottom right side of page)...

https://books.google.com/books?id=U4TBoJB2zgsC&pg=PA985&lpg=PA985&dq=axle+whine+howl&source=bl&ots=MXRWSoRMqk&sig=ACfU3U1Ud9Tt6xjZJ4QrK3GurPuqGh_fPA&hl=en&sa=X&ved=2ahUKEwjrvvfg8qzpAhVUrJ4KHfOvB_k4ChDoATADegQICBAB#v=onepage&q=axle whine howl&f=false

IMO, it's worth a shot, especially since these diffs are known to come slightly low on oil from the factory. It's on my list of things to experiment with.

 

Only issue now with noise is on a very windy day while driving against head winds. The wind noise becomes annoying as it hits the tonneau cover

 

Many people in this thread have tried different grades of gear oil with no change, the cause of the noise is supposed to be from a harmonic vibration.

 

The consensus: Toyota is aware. They tried to mitigate the symptom by reducing the amount of resonance entering the cab via TSB that applied to earlier model years. It didn't do much. They are still playing with spring options as of current model year. Resonance is generally not a difficult thing to remedy if one is able to find the source, you just change the mass or characteristics of the resonating part - according to an engineer from another field their guess is that Toyota isn't chasing this very hard or it would be fixed by now. New Tacomas were meant to include the mitigation measures but they do not probably because they do not work and consequently the cost not justified. People have tried friction modifiers, climbing oils, and heavier diff oils without success. Lifts etc will change a lot of things at once on the suspension so it's conceivable they would change resonating characteristics.

 

Did I read in here that a lift is a cure?
If so how much of a lift to get results?
My 2020 has started to get quite noisy between 50 -59. 6000k miles

 

Well, i just hit a bit over 2k miles. Truck is quieter than a church mouse when cruising 60 mph plus in the od gears. truck gets louder when the engine starts pulling 2500 rpm or higher up grades. Sounded like one of those rice rocket bikes.

 

I drove my father-in-laws 18 which is the same spec as mine but one year older. While I can get his to whine it is very difficult. As he said if you don’t point it out you don’t notice it. It’s so quiet in comparison, I need swap his out with mine. He did not agree!

 

I really hate hearing that some trucks are quieter than others of the same spec. It just enforces the idea that something is actually wrong with these diffs, rather than just a minor NVH issue.

Although it's possible your father in laws truck, being older, has different leaf springs or something else is different. They were experimenting with different springs around the 18, 19, and 20 MYs.

 

Mine seems to be getting worse. Was only 55-58 now its 38 and 50-61.

 

You have a lift or anything on your truck?
Getting desperate enough to try some aluminum blocks in the back with 5100s up front and MT tires. curious if anyone did something similar and suppressed the noise. Shame cause im a big stock fan especially since I have a 100000 bumper to bumper warranty, but the whine is like an icepick in my brain.

 

Has anyone tried insulating the axle tubes? Perhaps foam with tape wrap to test. I suspect the axle tubes are too thin, due to where they are mfg, cost cutting, something has changed in mfg that causes this resonating.

 

The low frequency nature (400-500hz) of the howl makes it difficult to block since the wavelengths are rather long. I don't think you would have much success wrapping the axle tubes with foam. Your best bet is to get some professionally made acoustic material like dynamat and apply it to the back wall of the cab, but even then, dynamat works best on higher frequency noises since its relatively thin material. Their spec sheets show little noise reduction in the 300-600 hz range.

I do think the axle tubes and pumpkin are transferring the noise and maybe amplifying it, but the only way to really fix that would be to make the metal thicker/change the mass properties. Probably also change the leaf spring densities and bushing design/material. Not exactly easy DIY changes! I think Toyota was on the right track with their TSB, but they just seemed to have given up on the problem which is rather annoying.

 

You think Toyota has officially quit trying to fix this reflection of poor quality control? I would feel better if I knew they were still working on a fix. What’s crazy is they continue to manufacture these trucks dam well knowing there’s a major harmonic cab noise problem. I hope their bottom line is worth the tarnishing of this trucks legacy.

 

As far as some toyotas being noises than others, i had to get use to the engine revving sound in my tacoma compared to the 4.7 tundra. I think overall my 19 year old tundra was quieter.

 

I just don't see how it would take them over 4 years to resolve it. They have some of the smartest engineers in the world working for them who could fix this rapidly if called upon and given enough resources. The fact that it's been going on for so long tells me one of two things: 1) The real fix would require a significant redesign of the diff, axle, suspension, frame, etc. (too much $$$), or 2) Not enough people are complaining about it/not losing enough sales to be worth their time.

I am concerned that some people have it on acceleration vs deceleration though. That fits more along the lines of a gear setup issue even though Toyota and other reputable gear shops (ECGS) have said its not the gear setup. I swear though... I'd throw my money at any company who could fix this noise once and for all.

 

Is the howling noise really only prevalent to the dd cab tacomas, or are the access cabs howling as loud also? I've got 2100 miles on my access cab taco, theres absolutely no noise of such. I've got the v6 engine sound, but thats about it.

 

I had it on both acceleration and deceleration. And the pitch changed as I increased or decreased throttle. And it was loudest going down long hills.

That’s why the pinion angle thing made sense to me. Going downhill, in theory, changes the geometry of the driveshaft/differential (gravity).

 

I really wanted to keep it stock, so if I put a lift and MTs on in desperation to overpower the sound, then Toyota comes out with a fix, I will be pissed.

 

They had a TSB for 17s & 18s. Mine allegedly has that in from factory. It still absolutely screams. I escalated mine to corporate, a tech came out, and guess what?
“Toyota says it’s normal”

They’re done trying to fix it