Remove the stop at the end of the track. Typical door stops are bolted to the wall at the end of the track or bolted up through the bottom and resting in the track itself. Use a sturdy ladder to reach the track. Remove the bolts with a socket wrench and set the hardware aside with any fasteners to be reinstalled.
Roll the door, with a helper, out through the open end you created in the slider. Keep the front edge supported and let the back edge down gently. Lay the door on a pair of sawhorses to allow access to the rollers on the top of the door.
Run a hose to the top of the ladder with a pressure nozzle and spray out the roller track to remove any dust and debris. Run a piece of beeswax by hand down the length of the inside of the track, rubbing along the bottom wheel channel to lubricate it for smooth action.
Spray the rollers with the pressure nozzles to remove any grime or debris that may be gumming up the wheels. Turn the wheels to check for easy rotation. Spray aerosol penetrating oil on any wheels that feel resistant.
Check axle bolts and snug down any loose nuts with the socket wrench. Apply a coat of white grease to the inside of each wheel against the axle. Pack it in with a cotton swab.
Reinstall the door in its track by lifting it upright and inserting the wheels of the leading edge into the track. Lift up on the back edge and roll the door forward until the rear wheels touch the rail. Lift up and slide the wheels into the rail. Slide the door all the way to the opposite end of the track and brace in place if needed to hold it.
Reassemble the stop by driving the bolts back into their original positions with the socket wrench. Test the door for proper operation, being careful not to slide heavy doors too firmly to prevent damage to the track. Apply more wax if needed.