Ford Super Duty Hub Lock Vacuum Line 7C3Z-7A784-C, 2005-2010

This is a replacement vacuum line assembly for the pulse vacuum hub lock (PVH) system Ford used on the 2005-2010 F-250, F-350, F-450 and F-550 Super Duty 4x4. It replaces Ford 7C3Z-7A784-C, 7C34-7A784-EB, 7C34-7A784-EC and 7C34-7A784-ED. It is molded to follow the factory routing from the PVH solenoid, near the passenger-side firewall and battery, down to the vacuum fittings on each front steering knuckle. The listing states the check valve is included.

On these trucks the front hubs are locked and unlocked by vacuum, so the whole 4x4 system depends on these lines holding vacuum. The factory plastic lines get brittle from heat, especially where they pass near the exhaust manifold, and they crack at the bends and at the knuckle connectors. Symptoms include a front end that will not pull in 4WD, a grinding or clicking noise from the front hubs, hubs that stay engaged after you shift back to 2WD, and a hissing sound near the firewall.

To confirm the problem, attach a hand vacuum pump to each line at the knuckle and at the solenoid end. A good line holds a steady reading. If a line leaks down, or you find cracks when you flex it, replace the assembly. Unclip the old harness along the frame and inner fender, disconnect it at the solenoid and at both knuckle fittings, and route the new assembly the same way. Keep it clear of the exhaust and steering parts, clip it in place, then cycle the 4x4 system and test drive in 4WD.