Front, I'd run it. Rear, I'd think about new gears. The rust runs into the the center of the contact patch and could cause a groan noise. Is there a backlash change when that part of the ring gear is in contcat with the pinion?
Was the differential full of water for a long time without moving the gear? It looks like it from the rust "line" across all the teeth.
83 Hilux SR5