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

For those that care i made a case with toyota and they said i can replace the diff if i want but its a hit or miss, even the new ones will have the noise he said it might be quiet or louder with a new diff. So i asked him if different fluid would help he said yes but has to be toyota approved fluid he couldn't recommend a brand as he works for toyota tech assistants.. This is my personal truck, im a toyota tech but i think i will live with it i dont feel like taking apart my truck with 500 miles on it, Going to order some redline syn rear gear oil and see if it helps.

 

What is your timeline for the fluid replacement? I'm sure there are a lot of eager owners waiting to hear the results.

Until that time, this is all of our rear ends: https://www.youtube.com/watch?v=1Isq_KJHriU

 

I'll get it ordered tonight from Amazon as no one local has it in stock. Hopefully by friday.

 

Y'all making this up

 

I thought they were to... until I noticed mine start around 55mph. Bullshit. Only 2,083 miles.

My truck is starting to sputter in the lower rpm range too... I'm flustered

 

Yes. And getting worse. 750 miles.

Trd off road. Auto. 2017.

 

New or different fluid most likely won't help. It didn't for me at least.

 

@smitty99 I have a hypothesis. Do you think the compound driveshaft angles could be causing strange wear on the ring and pinion? Some details: These trucks are taking a little bit of time to develop the howl, and it gets worse with time. Toyota is tearing these returned center sections apart, supposedly finding nothing wrong, putting new differentials in trucks, and having the same issue showing up. Important Note: the issue happens when the throttle is feathered. This detail is important. What if the real cause is the varying velocity of the pinion, due to unequal universal joint angles (between the sections), coupled with only a weak "staying" force, due to only a very light throttle being applied, is causing a gear slap oscillation (or the howl we are hearing)? Perhaps Toyota is only fixing the symptom when they replace the center section.

Fyi:

https://m.youtube.com/watch?feature=youtu.be&v=Idk3BVDVHq4

 

My replacement diff was howling as soon as I picked it up, and had less than 10 miles on it. I would bet that the "test drive" they did after replacement was only a couple of miles, and I don't know that this would be enough time to cause significant enough wear to result in the noise - but I guess it is possible.

 

Mine too.

 

That's good information Mace and fdbyrne.

 

The fact that the noise occurs at certain speeds is interesting. Mine has a sweet spot at about 45 mph. I need to do some measurements and calculations to see what component is resonating at that speed. Does anyone know the frequency of the howl?

 

Brad I think somebody else posted this video on the forum last year. Couldn't tell you exactly when and where, nor could I remember the hypothesis. If the FTS and Service Manager aren't lying to me, and totally speculation on my part, Toyota engineers must already know the root cause (though they won't share those details) and are working on testing out the field fix. Something must have delayed deployment of the solution however, because initially (IIRC) in August they told me it would be out within a couple of months. When October/November rolled around I emailed them for a status update and they replied it would be another 2 to 3 months. Maybe they're just slow rolling me or maybe they have run into some issues with the fix. I have no problems with the delay so long as they get the solution right the first time. Too bad they didn't take that same effort to rolling out this generation to begin with. We're driving the test bed version of this truck which really was barely fit for LRIP by defense acquisition standards.

 

with a 3.90:1 ratio rear gear, and stock tires, I am calculating about 351hz, for ring and pinion tooth mesh on my Tacoma at 45mph, if the issue is in fact a backlash gear mesh issue. I made a 351hZ sine wave using Audacity and played the audio. The sound is very similar to the howl I hear at 45mph. I am betting the howl is coming from the teeth on the ring and pinion.

 

Thanks for the reply smitty. Let's hope the solution isn't just a noise abatement.

 

If our gen 3's, run out of manufactures warranty, is this something they would cover(diff replacement), since they know this is a widespread issue?

Makes me think if I should have bought the extended warranty.

 

A leading contender for sound is pinion bearing preload problem. This is also a new design so it is equally as possible that it is a combination of components that just plain make noise - which seems to be the direction Toyota is headed in if rumors are to be believed. Rest assured given time they will find a solution. I am willing to wager that a 2019 tacoma will not have a howling rear diff. Less sure whether we can expect them to retro-fix all the 8.75's in the wild already.

 

I can swear l read somewhere that its not an all new rear but been in use for years overseas. It is obviously all new in the Tacoma and maybe they outsourced for cheaper parts.

 

Wow! Nice work man, you're definitely breathing different air than I.

 

Far more humid here in SC