I have an 8 3/4 742 rear, 3.23 Sure-Grip. I'm getting a high pitched noise on acceleration, either to maintain speed or increase speed. If I release the accelerator pedal, the noise goes away. The noise is worst at 45-55 mph and seems to decrease at highway speeds. The rear is in a 1970 Fury convertible. Tapered roller bearings on axle shafts are newly greased and endplay is correct. Rear does not make noise on turns. I suspect the noise is pinion gear or rear pinion bearing. Does anyone know how to distinguish between pinion gear noise and pinon bearing noise? I've heard that pinion gear is higher pitched, but could use some help on whether ring and pinion need replace. Thanks, Ben