No I've never seen a light come on for the diff lock tried several times with button pressed in and button out..no light. Owned the LC for 2 yrs
Bearings are easy to check, jack front wheels off ground and see if you can wiggle the tire from the 12 and 6 position. In my experience bearing roar can be heard when under acceleration as well as coasting.Great I'll ask my mechanic to try that.. do you have a suggestion why the humming started. I mentioned it in my original post.