I have a 05 Lariat SCREW with the 5.4 and 4x4. Just put new all season radials on and now notice a light howl (hum) in the drive train. The truck has 207K on the clock and has always been serviced the last 3 years at 3K intervals by Ford. Before then po (original owner) always had it serviced at 5K intervals. I believe the noise is due to the mileage and normal wear. Is it possible that changing the diff fluid would help quite the noise or, since I plan on holding on to it, should I have the bearings, seals, and fluid changed. Other than that the truck is in excellent condition and runs perfect. Any thoughts would be appreciated. Oh and yes I'm retired and on a fixed income but I already have new fluids and limited slip fluid.
TIA