The arrangement of brake system components that use fluid to transfer controlling pressure to the caliper is called the brake hydraulics. Without this transfer, your Ford F-350 Super Duty would be unable to reduce its speed or stop. These actions are important to both your safety on the road and that of other drivers.
A failing brake system is an accident waiting to happen, and you should never ignore early warning signs of malfunction. This might include the feeling of a spongy pedal (that is, the brake pedal compression is soft). Replacing parts immediately can prevent further Ford F-350 Super Duty damage. Keep your fluid levels high to avoid a problem, and bleed all air from the lines.