True locking differentials are not available from Ford, therefore, your Ford explorer does not have a true locker. A locking differential forces both rear axles to spin at the same time; however, the term "locking differential" is also often used to denote a limited slip differential. A limited slip forces both axles to turn when driving in a straight line, but when you accelerate into a corner, it removes power from one axle. Your Ford Explorer could have a limited slip differential.
Place your Ford Explorer into neutral and place wheel chucks in front of the front tires. Make sure the emergency brake is off.
Place a jack under the rear differential housing on the rear axle and jack the rear tires off the ground. Place jack stands under each side of the axle housing and lower the Explorer onto the jack stands.
Spin one tire counterclockwise (towards the front of the Explorer.) If the other rear tire spins the same way, you have a limited slip differential. If the tire rotates in the opposite direction, you have an open differential. Open differentials only place power to one axle, no matter the situation.
