Re: Identifing 4x4 part and problem
That part is the Pulse Vacuum Hublock Solenoid which directs vacuum to the PVH hubs to engage them in 4WD. In 1998~2000.5 Rangers, the PVH system shares vacuum with the HVAC controls and there is a reservoir to maintain vacuum to these two systems when manifold vacuum drops off. Common problems are a leaking reservoir or leaking PVH hubs. The location varies by year but I believe 2000 has the reservoir between the inner and outer fenders on the passenger side.
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