Rear Diff Fluid
I have been going over my 02 Ex with a fine tooth comb lately...Not sure if I am "nesting" as my wife is about ready to have our 2nd child and I want to get the Ex in shape or what...But I got a inkling to check the FT and Rear DIFF fluid levels today...I have never ck'd them before..(I know..Shame on me) but the Rear Diff was exactly 1 qt low. I went and got the 75w140 SYN. from Ford..It was about 20.00 for 1 qt..It brought the level exactly even with the fill plug hole. The magnet on the filler plug had some metal shavings, but not too much. I see in the manual it takes just under 4 qts of diff fluid. Would running 27k with a qt low on diff fluid screw anything up??????
I hope not...
Big Rig
I just changed mine out with $12.20/qt Amsoil 75w140. I've got only 21K miles on it, but the truck was manufactured almost 5 years ago now, so it was kinda old.
The real question: Why is it a quart low? Are there any visible leaks? If so, check the breather, there's a hose that runs up into the chassis, coming off the top/left of the diff. If the breather is clogged, it will push oil out any available seal

By the way, changing out my transfer case lube to Castrol Syntec, and the rear diff to Amsoil, I REALLY notice a difference in acceleration - and no I'm NOT nuts !
art k.
How did your Diff Oil look after 5 years???
Mine doesn't look to bad and it is 3.5 yrs old right know with just under 28k on it.
Mine is still Amber Yellow looking, just like the new oil from Ford I just put in..
Big Rig
By the way...Thanks for your input...
How did your Diff Oil look after 5 years???
Other than the limited-slip additive giving it a dark grey color, the lube was fine. No water, no bad smell (as far as gear lube goes, anyway!), etc.
I just changed it for the heck of it, and Amsoil was the cheapest I could get (wholesale)...
Funny thing... I wasn't going to remove the rear cover, I used an oil pump setup to pump out the gear lube through the fill hole. I was preparing to fill it up, using a Mobil 1 container, and had the plastic cap on the tip. I checked to see if I could get the right angle with it, and the plastic cap fell off INSIDE the diff... well, the cover needed to be painted anyway




I used to oil my bicycle chain, and man, I had the fastest bike in town.