Mystery grinding sound ... bearing or not?

Symptoms suggesting a wheel bearing:
-- audible "wrump" sound increasing with frequency as truck speeds up - audible even at 10mph
-- no sound when turning LEFT (suggesting left bearing)
-- no shake of the wheel

But:
-- checking all wheels by grabbing top and bottom (after lifting them) creates no movement.
-- taking wheel off (left) and playing with the disk brake and hub shows zero movement - bearing is very stable
-- all joints look good - no tears anywhere
-- I checked all u-joints and even changed the oil in the pumpkin - no effect. All stable, no movement at all.

The left bearing is a Timken replacement bearing with about 18,000 miles. The right is still stock. I am guessing this is indeed a bearing that somehow got maybe a "flat spot" which doesn't effect wheel lateral stability but creates noise.

Taco has 133k miles and its 2010 TRD off-road. Some towing use, some truck hauling use, some off road use. Majority still daily drive use.

Thoughts?

 

Did you grease the Ujoints?? I would try that first....

I had a similar situation with our Jeep that made a strange wrump sound. We checked just about everything and it ended up being the cardon joint needed grease.

 

When you lifted the truck and checked for movement, did you spin the wheel by hand and listen for noise? That can sometimes find a bad bearing. If you need one, I got em! lol. Just check my sig.