Constant Humming Noise

My 2008 Taco has a constant humming noise when rolling. Good Treads and have rotated religiously. When I rap it up, the engine sounds solid. 98K on the motor. Full synthetic done every 6500K. Any thoughts?

 

Wheel bearing is bad

 

No shit? Easy fix?

 

Nice reply....

 

Yeah that was bad. Thank you for the advice. I work in Agriculture and wrench on equipment daily. Never done a wheel bearing on a truck, only implements like disks, plows and such.

 

Could be any number of things in theory. Sticking brake caliper/pad. Wheel bearing. Differential issue. Drive line issue.

Can you tell where the humming is coming from?

 

Sounds like it's coming from the motor. Just a steady low hum. Truck seems to be running tip top.

 

Does the humming sound change at all with engine speed, or with vehicle speed? Important distinction here.
Or maybe it's the same all the time regardless of changing RPMs or vehicle speed...?

 

It stays constant with the engine speed. When I rap it up, the motor sounds solid.

 

So you can sit there in neutral and rev the engine, and the humming sound will change along with the RPMs?