8.25 noise

73 Dart Sport, 340, fresh 8.25 rear with Motive 3.91 gears and a Sure Grip. Part of a 4 year restoration. When driving I get a steady whine from the rear. Whine speeds up and slows down with vehicle speed. Did not hear anything with a stethoscope on the housing and the car in gear. Pulled the rear cover and checked backlash - the same all around and the wear pattern on the ring gear is near perfect. I can turn the pinion by hand and for about 3/4 of the ring gear travel it spins freely. At one spot, for about a 1/4 of the ring gear travel, it binds up. Doesn't spin freely but can be turned by hand. Any thoughts? Could it be a problem with axle bearings? Looking for things to check before I drop the rear end and pull everything apart.