I'm not sure what's going on here. When I accelerate to more than 30, it starts to whine from the front. When I take my foot off the accelerator the noise stops. I don't think it's the front wheel bearings, they were replaced a year ago, when I converted to disk brakes, and I think they would always whine regardless of acceleration. Could this be a ujoint problem on the front driveshaft (quadratrac full time all wheel drive)? Or pinion bearing issue in the differential?
The only other thing I can think of is maybe a vacuum leak.
This is whining noise and not a grinding noise. Anybody have any ideas?