New true-trac differential whine

Incorrect pinion gear depth. Period.
Can ya tell me about this one? Can hear a faint whine in a Dana 70 in a pickup starting at 55 and can't hear it anymore once above 65. Let off the throttle and it's not as loud but still there. If the radio is on just enough to hear the announcer talking, you can't hear the whine. That's how low the whine is. No noise on accel or decel, just cruise and between 55 and 65. Gear brand is Motive.