Could be many things. From a sticking vacuum switch on the transfer case to a broken transfer case or differential. You will need to start diagnostics on it. First check to see if the transfer case is engaging, You can do that by switching to 4X4 and then seeing if the front driveshaft is locked in. If it is then check the front axle interlock. It is cable controlled by a vacuum diaphragm located under the battery box. You can manually pull the cable and see if the front axle locks in. Just jack one side off the ground. In 2WD that wheel will turn, in 4X4 it won't. If those both check out OK then see if there is a vacuum signal to the 4X4 actuator when you switch it to 4wd. If not the valve on the transfer case may be bad OR a vacuum line going to it may be bad.
Thursday, October 2nd, 2008 AT 11:05 PM