Symptoms
The 2WD/4WD switch does nothing, the 4WD light stays on or off, or the truck stays in one mode.
The fix, step by step
- Selec-Trac shifts between 2WD and 4WD with engine vacuum.
- Trace the hoses from the engine to the reservoir, dash switch and transfer case, and test each with a hand vacuum pump.
- Replace cracked hoses, the reservoir if it leaks, and the transfer-case switch if the indicator is wrong.
- Fix leaking yoke seals and refill with fresh fluid: Team Grand Wagoneer says 3 quarts for an NP208, 228 or 229.
Tools & part numbers
- Hand vacuum pump
- vacuum hose
- multimeter
- sockets
- fluid pump
Where to buy the parts
Vacuum reservoir tank with mounting screws, 1974–1991Team Grand Wagoneer ↗Amazon ↗
Transfer case switch, NP208, 1980–1988Team Grand Wagoneer ↗Amazon ↗
Transfer case NP208/219/228/229 input & output seal set, 1976–1991Team Grand Wagoneer ↗Amazon ↗
100% synthetic transfer case fluid, 1980–1991Team Grand Wagoneer ↗Amazon ↗
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Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.