I’m trying to diagnose a noise that appears to come from the front drive train. Leaning towards front differential (4WD). it changes tone with gas pedal application. Front cv axles and bearings are new. With 4WD not on why would there be a change in tone in the front differential? Is it still engaged? Could this be rear differential echoing up front seeming to be the front one??? Hoping there is someone here with 4WD experience. Thanks in advance.

 

Fluids in diff and t case clean ? Are you testing on dirt or wet road? Dry road will cause noise and issues.

 

The front and back fluid was changed about a thousand miles ago and was sludges. Back more than front. Noise is present same on dirt or paved.

 

May need to get it up on a lift to run it and listen. U joints can also make noise if dry.

 

Thank you. I will try that.