Hum on deceleration

Some tires do make sounds other than the sound of the tread on the road surface. I had a set of BFG Rugged Terrains on my 4th Gen 4Runner that would hit a harmonic hum at certain speeds. Given that tires are hollow and encased in steel belting it makes sense that they would produce and resonate some harmonic sounds under certain conditions.

Tire noise will always be speed sensitive or dependent on the road surface though. Throttle input wouldn't have any impact at all.

 

Listen up everyone, no need to speculate.
Someone who actually knows whats happening has answered the question.
Thank him and move on.

Thats was a bit dickheadish but not every thread on tacomaworld needs to be full of non-sense.

 

For Toyota trucks I use the crush sleeve.

 

@BamaToy1997 I have discovered that my hum is not when I'm off the throttle completely, It's prominent while I'm at speed on the highway and only on the throttle a little bit.
Does this change your diagnosis?

 

Mine started that way too. As it got worse and louder it started happening while completely off the throttle. At this point I can kick it into neutral (manual) at 60 and I get the same sound all the way down to a little below 40.

 

Ok, great info.
Mine is a manual also.

 

It wouldn't be on the coast side of the gears then, it would be on the drive side. And with a manual transmission it COULD be noise inside the transmission itself. Can you get a recording of the noise for me?

 

Sure. I put something together asap.
Thank you

 

If its anything like mine, google 400hz tone. It can be "encouraged" to happen by feathering the throttle around 55-60mph. The range varies, but that seems to be the sweet spot.

 

So can you explain how this works? Is it a simple fix? I have an 8yr 125K warranty because they put out such a crap truck (I dont really want to lose that). BUT this howling is absolutely ridiculous.

If its a simple, straightforward fix, I would be all ears.

 

Yes, my howling range has gone from 55-60pmh to 45-75. I think I am hearing it below 45 now too.

 

@BamaToy1997
I put a recording together today buy the cabin noise makes it hard to pinpoint the sound we're trying to diagnose.

Hope this works:

https://www.dropbox.com/s/4o973kp0s9ji25p/Whine-Hum On Partial Throttle.m4a?dl=0

 

Sounds like dynamo hum, and you don't know where it's coming from, all you know is it's name is dynamo hum.

Older members will understand what this is.

 

It's the reason it hurts when I pee.

 

I just listened to your recording . Hard to hear with all the background noise .
If you are getting the hum while decelerating , turn the truck off in neutral at the speed where you get the hum and try to listen for the hum . This will eliminate engine noise and any transmission gearing under load .
Its the first thing I do on a test drive when customers bring their vehicles into my shop for a free test drive for a humming diff.
I agree with Mr Bama . Issues with coasting pattern in the rear diff . Seems to be a very common problem on the 3rd gen .
Start a poll at Tacoma World for the humming diff and force Toyota to live up to their mistake

 

This is a great idea.
Just to reiterate. For me, I wouldn't say the noise is occurring during deceleration.
It's while I'm at a speed 55+ MPH and on the throttle and at partial throttle, perhaps 10% throttle.

OP I apologize for hijacking your thread. If you prefer I start my own thread let me know and I will.

 

I was going to try this when I was out today and realized that for my case this reasoning doesn't track.
If the truck is off and in neutral it does not meet the conditions for my hum.
I need to be partially on the throttle to initiate the hum which requires power from the truck.

@BamaToy1997
After my drive today it sure sounds like it's coming from the rear of the truck. I need to be driving on flat road or on an decline. On an incline I do not notice the hum.
I was wanting to be able to give the dealership a theory from someone who has troubleshot and repaired these symptoms.

 

Your symptom is the exact same a lot of us have. Toyota replaced my differential and it didn't solve it. There is an extensive thread that smitty posted including videos from myself where you can hear it loud and clear, on both my first and second differential. The new differential was quiet for all of maybe 10 miles. Now it's back to howling loud enough to hear over a CD playing at volume 20.

Official response from Toyota? Sorry, we replaced the diff and it still makes noise. We didn't see any excessive wear on the first differential so it must be normal. Call us if something breaks.

I kid you not.

For a reference, my first diff was replaced at 8k miles, I'm now at 15k.

 

Wow
Now I'm concerned.
@BamaToy1997 Would you suggest having the rear diff inspected & repaired elsewhere?

 

No matter what you do, please call Toyota corporate and open a case. Voice your concerns and get it documented at the dealer. Toyota needs to keep hearing that this is unacceptable and that customers are considering no longer being toyota customers if this goes unresolved.

If you open a case too and have it documented you should be covered in the future, outside of warranty, if anything does happen. Not to mention part of a class action suit if enough people are affected and it comes to that.