Additional Testing For 4X4 Trucks

WARNING: This page is about a different car, the 2002 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

Check for any noise change when shifting the transfer case between 2H, 4H, 4L or into NEUTRAL.
With the vehicle at a complete stop and the transfer case in NEUTRAL, shift through all the gears and evaluate the noise at different engine RPM. Check for any noises in NEUTRAL at different engine RPM.