2002 Ford Explorer Codes

One less expensive alternative would be to get another rear from a salvage yard. Just make sure to get the same gear ratio as the one in the car now.

Rear end noises are generally expensive to repair. The gears are expensive, and setting them up is tedious and time consuming, and requires quite a few special tools. Once a ring and pinion become noisy and start to whine, they tend to stay noisy, even after resetting them up. Heavier oil may lessen the noise, but not by much.