Off-Road Ranger I
This is a pretty easy and inexpensive mod you can do if you have some mechanical ability and simple tools.how do u check where ur diff breather is
There's lot of posts about it, search the interwebs for "diff breather" or "breather relocation", something like that.
It just involves moving the vent on your diffs, and probably transfer case to a higher location.
On your Expedition, the vent might be located on a high point of your differential. You just remove that, put in a hose fitting, run some hose from that fitting up to a higher point, say in your engine room or up into a fender, and re-install the breather on the end of the new hose.
Make sure you leave enough hose length from your diff to your frame to allow for articulation. Not sure if your Ford has a live axle rear end or an independent suspension...?
I've summarized it a little too simply here, if there's a forum for your particular car, I'm sure someone has done it successfully.
g'luck!
Dan.