What type or rear differential fluid is in the 2001 ford f150?

The 2001 Ford F-150 useS75W-140 gear oil in the rear differential. This is a much thicker fluid than what You would expect to find in an engine or transmission because it is a much more confined area that can get very hot. A thinner oil would break down much faster against the gears so a thicker oil should be used. I recommend that You change Your differential fluid every 30,000 miles to keep the gears in the rear end protected and free from damage. The rear differential is the laSTSet of gears that the engine's power goes through before it reaches the tires and that can put a lot of stress and strain on the gears so it is important to keep them lubricated.