I was changing transfer case fluid today and just doing a quick look, I couldn't find an oil plug on my front diff. Haven't had truck long and have high mileage and thought it would be good to change the gear oil in it as well as rear. Anyone have a pic that might help? 2002 4.0. Thanks.

 

The front diff doesn't have a drain plug. For a really good draining, the front cover must be removed which means pulling the diff.

Another option is a fluid suction pump in through the fill hole. That is the approved Ford factory shop manual method but probably not the most thorough IMO. It seems really unlikely that all of the residue in the bottom of the case could be removed that way.

I added a drain to my front diff by drilling and tapping for a small plug. The problem is that the tapped aluminum case is quite thin and won't stand up to any abuse like overtightening. Since I'm the only one who works on it, my fix is OK but only just OK. The next time I have the diff out, I'm going to weld it up thicker and redrill and tap to make it more robust.

 

Thanks. I assume the fill plug must be on the driver's side where I just couldn't see it maybe?

 

Yes, driver side.