Fluid leak under my truck. Not sure of source

[Thump]

I noticed a slight bit of smoke from under my truck and figured it was something on the DPF burning off following a regen.
Well, notice a couple small wet spots in the driveway and decided I better investigate.
It looks almost like it's coming from the hard lines running from the differential pressure sensor to the exhaust system. The rubber portion of the tubes are dry. I don't know if those have any fluids in them, but it's a matter of follow the wetness toward the front and that's where it starts. It's dry on the differential pressure sensor and above (and all around) it. The fluid is predominantly on the passenger side, inside the frame rail. However, behind the t case it's slung frame rail to frame rail, under body to skid plate.
It's definitely slung all over my front ujoint for the rear driveshaft and under the body there, which had me thinking t case output seal, but it's dry and no evidence of nicks or wear to the shaft where it goes in the t case. The leading area of the t case output yoke is dry. The evidence of wetness there starts at the ujoint.

I can't get a color on it due to all the road crud mixed in and my sniffer is all stuffed up to the point everything smells like snot.
Being mostly sick, I didn't think to get pics before it got dark out. I've chased many leaking mechanical parts in my life, but this one is perplexing.

It's a bone stock 2011 3500 4x4 CC DRW with the 68rfe. I'm flummoxed unless there is liquid in those tubes to the temp port locations in the exhaust stream.
Thanks in advance

 

[Newsa]

Put some white or light colored,card board down over night and,see what it collects. Put a brick on it so it doesn t move

 

[Thump]

There's a thought. I have some poster board. Will do
The wife and rugrat will just have to go back to the craft store to finish her science project

 

[Thump]

I let the paper sit overnight and had one drip on the poster board. It's definitely not red, but doesn't look like oil, either. Can't smell, still... Also still can't upload a pic
Put the paper back under the truck and will let it sit again overnight.
I did drive the truck to get the trans up to temp and check the level. It was just at the top hole of hot on level ground, engine running in neutral.

 

[Newsa]

If the drip evaporates and leaves white powder (which you may or may not see against white poster board). It is def?

Edit: you have a 2011, it is not def.

 

[Thump]

I'm a 2011, no DEF

 

[Hoefler]

Slip yoke plug is leaking. It is a soft plug/welch plug installed to seal off the splines on the u-joint end.

 

[Newsa]

Is there a slip yoke plug on the output of the transfer case?

 

[Thump]

Following some reading over the last couple days, this is what I was considering, too. Especially thanks to the wetness at the ujoint, but not around the front of the yoke and output seal.
The wetness up the exhaust pressure tubes to their rubber lead hoses was the confounding part.
I'll take the degreaser and pressure washer to it and slather on some RTV as a check. Gotta find the breather port, as this getting blocked seems to be the normal cause for this issue.

 

[Thump]

I accidentally duplicated the post.

 

[Thump]

So, it is red in color.
I've degreased and pressure washed the heck out of the underbody. I then let it dry and sprayed the yoke with brake cleaner. Letting it dry before going to town with a brush and rtv.
Going to have to put it on the rack to locate and add a Jeep breather to the vent. Just can't see it where it should be on the tcase from my creeper.
Going to let the RTV SET up overnight before check and fill the tcase.

 

[Thump]

Well, either the fix failed or that wasn't the issue. Had a couple good days and then BAM! smoke and smell again today.
Won't have the chance to look at it until this weekend. Cleaned all my personal items out in the event it catches fire before I can go get a look. Without all that grime under there, ATF has an easier time lighting off is my co siderstion