Ford recalled the geared Torsen limited slip differential on the early 2002 model year manual FX4's because they were fragging in the field. Because no problems were reported with automatic trucks, the recall did not include them. IMO, this was rather stupid since the axles were the same regardless of transmission type (???).
If your truck has the manual transmission and t-case, the axle should have been replaced already at Ford's expense. Rumor has it that the replacement axles had a purple tag on the diff for identification. IIRC, the cutoff date for the recall was for trucks built before sometime in January, 2002. You can check the build date of your truck on the Certification Label in the door jamb.
If you have an automatic, you have no recourse through the recall.
Check with a dealer to see if there are time limitations on the recall - sometimes there are no limits, especially if the recall is due to a safety concern.
Having the 4x4 light stick on the manual trucks is a common problem caused by a sticking switch on the t-case. Automatics get the signal for the dash lights from the 4WD Control Module.
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid