My 2003 F150 has had a whining sound for a little while and now today it has started a very light chatter when not accelerating. I finally pinpointed where it is coming from and I know I need to take it in ASAP, like tomorrow. I was just curious if it would be a big bill or if its just a diff grease and additive change. Any advice is definitely appreciated.

 

MAN IT IS HARD TO GET ANSWERS AND/OR HELP AROUND HERE. so i will give you my 2 cents. i would start by changing the diff. oil. after that if it is not back to normal i would check the bearrings and seals.

 

yup it could be in need of oil but i am pretty sure that year had a problem with the bearings going!!

 

https://www.f150forum.com/f6/hello-all-im-new-big-problem-11679/ try this or this

http://www.fordf150.net/forums/viewtopic.php?t=56834 this one is the first one I started, but I came to f150forum.com and recieved a lot more help.

 

i changed oil in rear end and test drove in four miles at about 45mph. Got back home and oil was everywhere. Front seal is shot. Took diff cover back off and ring and pinion have wear. Neighbor told me to change ring and pinion because everything else looked fine. If i change the front seal and bearing on the rear diff. and keep the spacing the same on new ring and pinion will that be a problem? Or will i be better off taking it to get spaced by a mechanic? Or best bet a whole new diff. from salvage? All help is greatly appreciated .

 

if it were me i would buy the haynes repair manual. then i would try to do it myself and if it failed then i would take it to the repair shop.

 

^^Haynes manual only tells you how to change the seal. It tells you nothing about shimming, or backlash. I would take it to a shop. From my experience, even changing the seal is a PITA. If you dont have the tools to crush the crush sleeve, you risk doing more damage. If you read my threads I posted, i was in the same boat you were. Luckily I didnt have to do any shimming. Just yanked all bearings, put new ones in, and viola', no more howling. Cost me just over 200 for carrier, pinion axle bearings, and all seals.
Check for slop in carrier side to side and front to back. If you pull the cover, mark the gears, and check wear notations.
IMO, you risk this problem again buying from a junkyard.