What was that noise my truck was making

2015 SR5 access cab, V6, auto, 4WD, tow package. 59k miles. Late for a couple oil changes, but all the 15k interval stuff was done at the dealer and I go to Jiffy Lube a lot.

Factory mechanicals, I have added offroad lights, heated side mirrors and hardwired my GPS. Otherwise all stock.

I noticed the other day, Christmas Eve actually, a rubbing or thrumming or humming that was loudest around 45mph, easily audible with the radio off from 40-55mph. Goes away above 55mph.

Counting one one thousand two one thousand @ 45 mph the thrumming lasts for "one one" and then silence for "thousand two one" and then repeats. I come up with about 2.5 seconds for the total noise cycle, about 0.8 seconds for the actual thrum.

At 45mph that is rolling about 165 feet with the thrum audible for about 53 feet of that.

Tires are Nokkian Hakka 9s on a spare set of factory rims, about 27" in diameter. Seems like the sound was in front of me to my right, I could sometimes feel it in the accelerator pedal but not in the steering wheel.

I was thinking I must have dropped a balance weight. Never had an out of balance situation feel like this before - and then I figured out it was intermittent.

When I would accelerate to 45 in 4WD with no thrum, and then shift to neutral and coast still no thrum, and then switch to 2WD, wait for LED to go out, shift back into drive, thrum....thrum...

So that, to me, ruled out brakes and tires, and then it went away completely. I couldn't get it to make the noise today - and I realized we have been down in the -30s Farenheit up here since Christmas eve, today it has warmed up to -12dF.

When I romped on it in 2WD it drove like it was in 2, when I romped on it in 4WD it drove like it was in 4. Going in for the 60k service in the next couple weeks, certainly I will ask the dealer and I have the platinum warranty.

Is there some kind of clutch system in the transfer case maybe? Is this a nuisance noise or impending disaster?

Thanks

 

The needle bearing most likely

 

YUP ^^^.

 

Your truck was mad cause you took him out frozen. His balls got sucked up into his belly, I’m sure that was the noise,

 

Sounds like front driver's side differential needle bearing. Look up ECGS bushing.