A friend of mine bought a 2006 TB with a problem in 4WD system. There was a "service 4WD" light on and the error code pointing to the front axle disconnect. We put a new front axle disconnect and the actuator; it cleared an error. However, the front axle is still not completely engaged in the "4Hi" mode. We heard some clicks from the front axle and thought that the problem is in the front differential. We replaced the front differential today, and now it seems that sometimes the axle is locked and sometimes not. The "new" differential is supposedly OK; we also crack opened the old one and did not find anything bad with it. With a "new" differential, after several minutes of "tests" on a slippery ground, the system refuses to enter the 4Hi mode and, again, the "service 4WD light appears". As I said, we already replaced the axle disconnect and the differential. What is left is the transfer case... Is there a possibility that the clutches of the transfer are bad and slipping? And, after several minutes of slipping the transfer overheats and does not allow the "4Hi" mode anymore? The problem seems more mechanical than electrical. Do you guys think the transfer case is bad?