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

Yeah, I have heard the noise comes back for most/all people who have received replacement diffs.

Logically, I tend to think Toyota is on the correct path with their harmonics TSB given the fact that many people have reported positive results, and that the TSB simply changes out the leaf springs, adds some noise insulation, and puts a couple revised cab mounts in place. Clearly the source of the problem is the rear diff vibration, but perhaps the way the gears are cut in these diffs makes them susceptible to noise. That would make sense to me.

I have a hard time believing that the diff supplier is screwing up on over 50% of the differentials they manufacture, and have been doing it for years. Seems unlikely, especially given Toyota's level of quality control, and the fact that they could assume serious liability should these diffs start failing on the road and causing wrecks.

Regardless, I wish Toyota would stay consistent here.

 

I can tell you for a fact from my line of work that you’d be very surprised about some of the decisions that are made on a day to day basis to not address certain issues. Look no further than the Remington fiasco that went on for literally 50 years regarding their Model 700. A simple few extra nickels would have prevented unintended firearm discharges but they chose to not do it, at first arguing costs and then others said it was more about avoiding litigation (not admitting an obvious problem). Toyota also got caught with their pants down on the unintended acceleration cases. A buddy of mine got them for $30 plus million on one case and they were clearly guilty as crap. Then again, I honestly don’t know in this case. I’ve yet to hear of diffs grenading so maybe they are just noisy? I truly don’t know.

 

My dealer suspected the diff oil was too thin in the factory fill. Got too hot and damaged the gears. My replacement diff was filled with 75x140. Been quiet for 60 K.

 

That theory would assume the diff manufacturer did zero testing of these diffs whatsoever with the factory oil. Highly unlikely. Heat management is basic stuff.... and arguably the most important performance criterion.

Also, thicker oils are less efficient at transferring heat than thinner oils.

 

Im going to get funny looks for this. I was having this issue. It was driving me crazy. I recently changed my differential oil with Mag 1 75w90 gear oil as routine maintenance and the noise went away. Not saying this is a fix. Not sure wtf was going on, and I have no explanation for it because this logically makes no sense. I recently did this at 60k and at 30k I had done the service with Lucas 75w90 gear oil. Just thought I'd share my experience.

 

I'm changing to 4.88 gears. For sure after break in, I'm running Amsoil 75W-110 in back and

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 in front. I do think less viscous than 75W-90 is asking for noise and premature wear.

 

Wow, I have 3600 miles on my 19.. we're like twins. Hope they solve our issues man

 

Sometimes, the proof is in the pudding. Do some research on 75/140 oils.

 

Not so much "got hot" but more likely the inability to maintain a fluid film when hot, AW and EP additives were not up to the task asked of them and some premature wear/damage occurred and continues with the 75W-85. Which I suspect while initially meeting specification, shears like crazy.

So are you saying yours was noisy then quieted with 75W-140?

Amsoil recommends

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90. Not 75W-85.

 

Noisy, yes at 59-61. It was replaced under warranty with 75x140. Quiet for 60k.

 

Yea I wasn’t really that worried about, but if there gonna fix it let em. The 17 that I sold was worse than this one. So guess we will see

 

Thanks. Not the first time I have heard this.

 

And I questioned the Service Manager about the heavier oil and he explained he's been dealing with this since 1989!

 

Another interesting academic paper on axle/differential whine (if you guys are extremely curious, or bored)

https://pdfs.semanticscholar.org/1404/a12c9dc2faa75c183d8a7be5f9f8e911110d.pdf

Of note:

 

At this point I hope my dealer does what they did for @Patrick1046. Replace Diff and different gear oil. Couple of local guys with Tacomas have zero noise. Seriously frustrated . Also can’t believe 2020s are having this problem. Speaking of 2020s, any updates on those?

 

I know this is apples to oranges, but I had a 2005 WRX with a very similar whine at highway speeds, it had a bad bearing and when they replaced it the noise was gone!

 

What model of Taco do the local guys have?
Have you personally driven in their trucks to confirm?

Some people simply can't hear certain frequencies, or are not tuned into the sound.

 

Both were 2018 Trd offroad dcsb. I’ve driven only one of them. 11k miles on it.

 

Do you know if it has upgraded or non-stock tires? Lift? Any suspension mods?

All of these can change or eliminate the noise.

 

Drove it while stock, no noise at 7K, now lifted on icon stage 4, new leaf, trd cai and exhaust, still no noise