OK so - I had the rear axle bearings replaced, but I’m still hearing a rotational scraping noise while moving (whether gas is applied or not, or whether braking is applied). Gets slightly louder the faster I go. But when I turn, the noise goes away. It’s hard to pinpoint where the noise is coming from. My wife swears it’s in the front; to me it sounds like it’s in the middle (so it would be being transmitted from the source).
I took it back to our mechanic, but he can’t hear it very well - he admits that his hearing is not what it used to be (he’s in his 70s). Only thing he hears is “gear noise in the rear”… meaning he’d have to replace the differential in the back which would be prohibitively expensive and not worth it. He said I should come back in a couple weeks when his younger employee will be back so he can listen for it.
Trying to pinpoint the source of a noise can be very frustrating. Did this noise exist prior to the wheel bearing replacement? The fact that the noise goes away wen you turn usually points to a wheel bearing. Have the front wheel bearings looked at, also.
I think this truck has rear disk brakes. The rear splash shields for the disk brakes rust pretty badly and bend very easily when rusty. The rotor may be lightly rubbing on one side or the other and when cornering there is quite a bit of axle side-play so it moves enough to make the noise go away.
Look underneath and any shield in the rear that looks a bit too close to the rotor, lightly bend it away and test to see if the noise goes away.
My first guess is what @Mustangman suggests, some kind of brake-part interference, likely the splash shield. OP could do an experiment, first get the noise to occur while driving, then shift into neutral and coast. If the noise remains it is in the power-train, but after the transmission; if the noise goes away, the noise source is probably in the transmission and/or engine.
I’ve had a sticking caliper cause a constant scraping noise. The good news is that an inspection of the pads through the peep holes may show asymmetry in the wear between the pads, making a dragging pad obvious. Cleaning and lubing the slides is the usual suggestion, and it’s worth a try, but in my experience that’s usually a temporary fix. That is IF the inspection shows uneven wear on the pads.
Can you feel any vibration in the steering wheel? turning and the noise going away is a possible indicator of a front wheel bearing, I had one instance where the outer pad for the disc brake was fine but the inner was toast, have them check inner pads, if fine, then find a mechanic with a stethoscope to check wheel bearings
I had a scraping noise . I actually pulled over & looked under the car to see what was dragging . Turned out to be right front wheel bearing . Can’t remember if the noise went away when turning or not .