2004 Truck. Engine Size : 5.7 liter Question: 4x4 not working . Does not switch over when I try to engage it.
It would help if you mentioned the make and model of your vehicle, and if you have electronic 4WD, or have to shift it into 4WD manually. If it's electronic, you could have a bad switch, or a bad actuator on the front axle. Either electronic or manual, you could have a mechanical failure inside the front axle housing that is causing it not to engage into 4WD, like broken gears or axles, mis-aligned parts, etc. If the problem is with the transfer case, you could have a bad encoder motor or a mechanical failure inside the transfer case. On the electronically controlled systems, there is a main control module that could be bad as well. You're best bet is to get it to a shop for diagnosis.