Does anyone know what kind of gear oil to use in the rear end of an 01 Sport Trac? I found the plug to the front and I can't read most of what it says on the tag. Can I buy it at Auto Zone or somewhere?

 

Rear Axle takes 2.9-3.1L (5.5-5.8 pints) of Motorcraft SAE 75W-140 High Performance Synthetic Rear Axle Lubricant Refer to Footnote 7

5. Fill to 6 mm to 14 mm (1/4 inch to 9/16 inch) below bottom of filler
plug hole.

7. Vehicles equipped with Traction-Lok axle require synthetic rear axle
lubricant. Rear axles containing synthetic lubricant are lubricated for life.
These lubricants are not to be checked or changed unless a leak is
suspected or service is required. The axle lubricant should be changed
any time the axle has been submerged in water.
Add 118 ml (4 oz.) of Additive Friction Modifier C8AZ-19B546-A or
equivalent meeting Ford specification EST-M2C118–A for complete refill
of Traction-Lok axles.

You do not need to use MOTOCRAFT lubes, but you should use a quality lubricant. Don't forget the friction modifier...