Need Help With Diagnosis Please

Hey guys this is my first post, thanks in advance for your time.

My truck is a stock 2020 Tacoma.
The only thing that isn't stock is the tire size. They are about 1 1=2" thicker than stock tires.

My truck has always been taken into the dealership I purchased from for maintenance. The truck has 106k miles. I've followed all guidelines from dealership as far as any necessary maintenance.

I have had multiple techs ride with me, and dig into the truck without any answers as to what the issue could be. The head tech said it's something he's never herd before.

What is happening is sometimes say 25% of the time when driving when the rpms are not idle, and not high when the accelerator is pressed I will hear this low hum or growl sound. I can feel the accelerator pedal vibrate when it happens. This also happens when in 4wd.

I have had the techs check the ball bearings and ball joints they both look fine. I have tried the highest octane fuel for a month straight.

Anybody have an idea of what I can do to fix this?

 

My guess was needle bearing, but that doesn't make sense if it goes away in 4wd.

 

Sorry if I wasn't clear, the problem persists even when in 4wd.

 

I should've worded my post differently. I meant my needle bearing theory doesn't make sense if it goes away in 4wd like you said. Sorry for the confusion, and good luck! Keep us posted when you get it figured out.

 

I had something similar in my 2015 Grand Cherokee. An intermittent roughness and low sound. Ended up being motor mounts that were toast at 75k miles. Do you feel it in your steering wheel at all? Or just the accelerator pedal?

 

It doesn't make the truck feel any different besides the accelerator pedal vibrating.

 

I'm going to need to get that checked then it sounds like it's a possibility of being the issue.