What's the 2003 Ford Explorer rear differential fluid type?

The 2003 Ford Explorer uses A75W-140 differential fluid. This fluid lubricates the axle and is formulated to work under a lot of pressure. It is generally thicker than engine oil which is more formulated to work under high temperature conditions in the engine. The differential fluid is also known as gear oil. It is important to keep this fluid topped up, or there might be excessive friction in the axle, leading to accelerated wear and tear, as well as outright damage. It is recommended that You change this every 30,000 to 60,000 miles. So You might only have to change it a few times in the life of the car.