i drive a 2004 chevy silverado 2500hd 4x4. my truck has a unusual humming coming from under the front end, i checked the front differential fluids and it was dry. i put a bottle of gear oil in it but the humming is still there. do i need to put more in, or is it something else?

 

Hard to say without hearing the humming (maybe it just wants to be a Hummer ), but my WAG would be you now have a bearing or something going out due to not being lubricated. Does it always hum or just at certain speeds/RPMs?

 

no it dont hum at certain speeds it hums at any speed and it dont matter where the rpm gauge is, the faster i go the louder the humming gets. its possible that its a bearing but i still think that its the front differential, its still low on gear oil, im going to top that off and see what happens then

 

Chances are if you ran it out of grease you may have damaged the brngs in the diff. If filling it stops the noise you better look for the leak that caused the problem.