Rear Differential
 

I've looked, but I don't see any information on how to change the fluid in the rear diff on a '03 Expedition. Looks like a daunting task as there is a box beam directly behind it. I see the bottom plug, but what about the fill plug? Anyone out there ever remove the rear plate? I've done this with PUs before, much easier. 91K on the ODO and don't know if this has ever been changed. Thanks.

It's an easy job, everything is easy to get to. The fill is further up towards the drive shaft, follow the housing forward, it is a 3/8" square drive. Driver's side I think. Make sure you can get the fill out first before you pull the plug.

Mine had a fill plug on the forward driver's side of the diff. It used a 3/8's square drive.

I suggest removing the spare tire first. The amount of working space doing that gives you is amazing.