I have a thumping issue with my Dana 60 front end when it's engaged.....It's a steady thumping sound and it changes with the road speed. I'm 99% positive it's coming from my stub axles at the knuckle. I put new inner spindle bearings in it and stub u-joints when I put the axle under the truck. I can move my stub shafts up and down a lot.....Could it be that I need new locking hubs or maybe something is missing in them like a spring or shims? They are stock Ford manual locking units and they work good but they are pretty rough looking. I'm thinking it's something simple but I've never had a 4wd do this to me before....I don't think it's my differential - It really sounds like it's coming from the wheel ends.