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Could be a wheel bearing I changed out both of mine on my 02 and the passenger side just kinda squeaked but the driver side had the usual whining sort of noise. Easiest way to find out is take the tire off and and the caliper along with the pads (so that you dont hear the brake pads squeaking and replace a wheel bearing for nothing!) and spin the rotor if you can hear a squeak or whistle its the wheel bearing. An easier way to do it is to see if the whitling gets louder when you turn the wheewhile driving. If so it is probably the bearing. As far as the filter goes go in at the front driver side of the truck and right on the other side of the frame you will see it and it drops right down.
I have a 03 4wd Lariat with 108K. Just chged front wheel bearings. To check if it's bearings, get up to 30-40 mph and do gentle s turns. The sound should stop as you "load up" one side and then the other with the s turns. That's the side with the bad bearings. I chged both sides because I figured the other would need it soon anyway.