1999 F250 4x2 - was stored for 3 months and when I tried to move it - the right rear wheel turns but the left rear wheel won't turn. Took off the brakes and caliper - still won't move. I can move it maybe 1/2 inch but clunks to a stop. Any ideas???

Hello, The rear rotor has 2 sets of brakes on it. The other thing is to look for slight movement in the driveshaft when it clunks. Depending on the rearend, some have to have both rear wheels off the ground to turn each side. And of course the trans in Neutral.

With the rear wheel you have an Emergency brake and a drum brake inside the center of the Rotor.
The rear of the brake backing plate has a rubber plug which is covering the Star-wheel adjustment for those drum brakes. You can try to loosen the Star-wheel to disengage the Emergency brake shoes. You can try pulling the brake cables toward the cab, to loosen the cables.

If this does not help, your Emergency brake shoe probably rusted off the brake mount and is jammed inside the drum. The linings fall off the metal like banana skins. I can tell you that if the Emergency brakes are a State safety requirement, you need to consider new rotors because the drum portion is usually trashed with rust.

I hope my Solution is very helpful to you.