I only notice the noise at speeds above 35mph. It might make the noise at slower speeds, but I can't hear it. I can feel vibration in the steering wheel and the floorboard at 60+mph. Steering one way or the other does not impact the noise.

I just crawled under the truck and was checking out the cv axles. The boots are in good shape, but I noticed the right side has a good bit of black "grime" where the inner portion goes into the silver shaft (I'm sorry, I don't the correct terminology for that part). Is it possible that the black grime is grease leaking out of that connection? Is that evidence of a bad cv axle?

Thank you for your help!