Hum on deceleration

Good info, makes tons of sense. I think I thing gave some inaccurate internationan. So I need to restate my problem.
I get a whining from the diff when I "feather" the gas at around 54 to 58 mph in fifth or sixth gear. That is on both the drive side and coasting side of the gear. Now the truck started doing it at 500 miles on the odometer and now at 1200 and the sound is still the same.

 

I'm experiencing a howling type noise as well. I hear it most when I am slowing to a stop say from 50-60 and it stops just before I stop. The howl seems loudest at about 15 to 20. I know its not tire hum cause its not consistent with rpm and speed.

07 TRD 4x4 Auto

 

Reporting back as promised.
I changed my rear diff fluid today and added the Lucas product as well.
I followed @BamaToy1997 instructions with the break in procedure afterwards.
At this point the noise is still there when feathering the throttle.

The drain plug had lots of crap stuck to it.
I was surprised as to how contaminated the fluid had become in 4300 kms.

 

Did the Howling lessen at all afterwards or did it make no difference?

 

well f*ck

I was hoping this was a magic bullet.

 

My experience was that I would have a whine or howl wheb feathering the throttle starting at 50mph and above. The faster I drove only changed the pitch of the sound. Many have expressed the 55mph sweet spot that it's the loudest, that was not the case with me.
After performing the fluid change and break in procedure my immediate response to your question is that now the noise seems to me loudest at 55mph like others are experiencing.
I will report back after driving some more tomorrow.

 

Me too. I honestly don't view this as a failure.
The fluid in that diff needed to go bye bye. It was filthy. Just knowing there is clean fluid in there makes me feel better.

 

Someone was saying a heavier weight oil might fix the sound.

That might be worth trying in the future. But there are warranty concerns.

 

I know this really is Toyota's responsibility, but if I had a gear shop I trusted (not saying I don't but I haven't looked around yet) I would pull the rear pod, give it to them and ask them to inspect it and get back to me with what is responsible for the noise and a solution and estimated cost.
Don't get me wrong @BamaToy1997 has already stated what is likely the culprit, but as I'm sure he would agree, there is no replacement for diagnosing a problem by having the item in your possession to inspect and draw conclusions based on your own facts.

 

I wonder who the Vendor is that is supplying the Gearsets to Toyota?

 

I think it's GKN Driveline.

 

I get the hum at 15-25 mph but its not a constant hum, its on deceleration or braking and it comes in revolution. on and off on and off. its a humming sound like womm womm womm... haha best way to describe this strange sound. I think its the dif, I had them check the fluid to see if it was low, both the front and rear were at the correct level according to the dealer. I also get a pop from 2-1st gear when its cold and i notice the hum when its colder as well. less when the engine is warm. hunting down the ghosts in this truck is a chore. the advisor said he thought it was a wheel bearing.

 

I found this and thought it was interesting.

https://www.autonews.com/assets/PDF/CA10079085.PDF

 

Update:

After some driving (about 50kms) my conclusions are that the hum has decreased in volume across the whole speed range (50mph+).
It's only noticable at the 55mph speed and even then it's considerably quieter than it was originally.
It seems like driving the truck is helping the product do it's thing.
I will admit I thought originally that it was just in my mind. I want it to work so hence I hear the noise decreasing. I do not think that's the case. It really is quieter. I'll keep reporting back

 

Glad to hear that, hopefully it will continue to decrease in sound.

 

I dropped my truck off today for this and the dealer said it was the LCA plugs TSB. Parts were ordered. I told them its not the cause because feathering the throttle doesn't change the wind speed to make the noise disappear.

 

Thats great news.

GKN Driveline is the manufacturer of the electronic locking rear differential. I wonder if we could contact them for extra advice. They might tell us to pound sand, but they might be able to provide some insight.

 

Toyota will tell you it's normal operating characteristics of the truck!

 

They try to tell everyone issues are normal.

 

Told ya!