I have a 1994 Ford Ranger 4.0 V6 4X4 with manually locking hubs. Whenever I drive with 4X4 engaged (at any speed) there is a high pitched noise emanating from the front of the truck. The best way to describe this noise: A whistle from boiling water in a tea pot. All the fluids are at normal ranges and the truck only has 68,000 miles. This only happens when the hubs are locked and the 4X4 is engaged. Any suggestions?
Have you lubed up the U-joints in the front driveshaft lately? Ever? I’d guess that’s the most likely culprate-- it’s supposed to be lubed every other oil change or so, but nobody ever actually does it. Lubing it now might fix it, or it may be too late.