Mile Marker 503 4x2 Conversion Kit & Accessories for Ford & GM 203 N.P.

NP203 4x2 Conversion Kit with 423 Hubs Mile Marker NP203 4x2 Conversion Kit with 423 Premium Hubs delivers a complete heavy-duty solution for converting factory full-time New Process 203 transfer cases into efficient part-time four wheel drive systems. Designed for 1973 to 1980 Ford, Dodge, and GM 3/4 ton trucks equipped with the NP203 transfer case and Dana 44HD front axles, this kit eliminates constant front axle engagement while preserving drivetrain strength and reliability. Factory NP203 systems were engineered for full-time operation, keeping the front drivetrain engaged at all times, increasing wear and reducing fuel efficiency. This conversion kit replaces the internal differential components, allowing the transfer case to function in true part-time mode when paired with manual locking hubs. Included Mile Marker 423 Premium manual locking hubs provide durable engagement and dependable axle control built for heavier 3/4 ton applications. By disengaging the front drivetrain during normal driving, this system reduces unnecessary component wear, lowers parasitic drag, and can improve fuel economy while maintaining full off-road capability when engaged. Engineered with precision-machined components and backed by decades of drivetrain expertise, this kit offers professional installers and restoration builders a proven modernization solution for classic heavy-duty trucks. Built for strength, durability, and long-term performance, Mile Marker restores control and efficiency to your drivetrain without compromising capability.