Seems to be limited to the area you see here. Is it coming from the seal around the drive shaft? It's a 2004 F150 (new body style) with 4x4 - 103,000 miles. It's been very dry and no leaks under my truck since new so this caught my attention when I saw it recently.

 

Im thinking one of a couple things. Sometimes on these trucks the seal between the tranny and transfer case leaks and puts extra tranny fluid into the transfer case. If there is too much fluid in the t-case it might be pushing a little out the output shaft seal and getting on the case.

Or...The fluid on the t-case is low and the oily air in the t-case when expanding from heat pushed past the output shaft seal and getting on the case.

Or the output shaft seal might just be leaking a little.

Check your tanny fluid, see if its low which could point to the seal between the tranny and t-case is leaky and the tranny is pushing fluid into the t-case. Also if this was happening, if you pulled the fill plug on the t-case which is in the picture you would get extra fluid pour out. Normal t-case fluid level is just below the fill plug hole.

Or you can pull the fill plug on the t-case and if fluid doesnt come out stick your finger in and see what the level is, if you cant feel fluid the t-case fluid might me low.

If the tranny fluid is fine and t-case fluid is fine your output shaft seal might just be leaking enought to let a little fluid out and allow if to get on the case, but not enough to drip on the ground.

And one more thing, the gasket for where the cone shaped part of the case bolts to the rest of the case might have a little leak in it.

If you end up trying to figure out which seal or gasket it is, clean everything up and drive it a bit and then check again to see where the fluid is actually coming from, also when you clean it looks for tiny crack in the t-case. Had this happen to me on my explorer.

 

Thanks. I'll check it out

 

Tranny fluid is full.

What size tool do I need for that transfer case plug? Is it the end of a 3/8 extension or a special tool/allen wrench?

 

Ok I got the plug out and it's full. I cleaned up the transfer case and I'll keep an eye on it. I do need to change the fluid in the tranny and transfer case. It's been in there for 100k miles now!

 

maybe need a replace seal by transfer case rear output shaft

 

I wonder if it's coming from the drive shaft seal. If it was, I would expect the fluid to blow rearward.

 

I just recently had the same leak. Went to the dealer and they replaced the transfer case seal and the output shaft seal. My truck had a line of splattered fluid on the underbody caused by the output shaft seal.