* Low gear oil: The differential needs the correct type and amount of gear oil to lubricate the gears. Low oil leads to excessive friction and the whining/winding noise you describe.
* Worn gears or bearings: Over time, the gears and bearings inside the differential wear down. This wear causes increased friction and noise, particularly noticeable under load (like when reversing uphill or slowing down).
* Damaged ring and pinion gears: These are the main gears in the differential. Damage to them can create a significant whining or grinding sound.
* Differential clutch pack issues (if equipped with an automatic locking rear differential): Some Explorers have limited-slip differentials, and issues with the clutch pack can cause a loud noise.
Do NOT continue driving the vehicle with this sound. Driving with a failing differential can lead to catastrophic failure, potentially causing damage to other components and leaving you stranded. The longer you wait, the more expensive the repair will likely be.
What you should do:
1. Stop driving the vehicle immediately. Only drive it if absolutely necessary to get it to a safe location. Do not attempt any strenuous maneuvers.
2. Check the rear differential fluid level. This is crucial. Look for your owner's manual to find the location of the differential fill plug. If the level is low or the fluid is discolored (dark brown, metallic particles), the problem is likely related to low fluid or worn components. However, simply checking the level won't fix the underlying problem.
3. Take your vehicle to a qualified mechanic or Ford dealership. A professional diagnosis is necessary to pinpoint the exact cause of the noise and recommend the proper repair. They will be able to inspect the differential, check fluid levels, and determine the extent of the damage.
Ignoring this problem could lead to a much more expensive repair down the line. Get it checked out as soon as possible.
