1999 Ford F Series Trucks Differential Spool F-250 Super Duty - 4WD - Dana 60 - w/ 35 Spline Axles - Spartan Locker - Installs into standard open carrier case - Front guaranteed to replace your current 1999 Ford F Series Trucks Differential Spool F-250 Super Duty - 4WD - Dana 60 - w/ 35 Spline Axles - Spartan Locker - Installs into standard open carrier case - Front. 1999 Ford F Series Trucks Differential Spool comes new OEM 1999 Ford F Series Trucks Differential Spool aftermarket new 1999 Ford F Series Trucks Differential Spool of remanufactured 1999 Ford F Series Trucks Differential Spool F-250 Super Duty - 4WD - Dana 60 - w/ 35 Spline Axles - Spartan Locker - Installs into standard open carrier case - Front.