I have a 1998 300 explore 4x4 that is making a grinding sound in front end. This sound is not always present. Any help will be greatly appreciated!

 

First thing check/change the hub fluid if you haven't done so. If either hub is dry,could be the source of the noise. Plus bearings in the center or front eccentric housings could be worn making the noise especially if they are greased periodically. The center eccentric bearings(by the right floor board) was the one I had the most wear on. Seems like a lot of people never greased the fittings. OPT