2nd Gen leak on underside of bed

After many months of monitoring this, I'm still unsure where this leak is coming from. The fluid is pinkish. It never leaks on the ground and doesn't touch anything hot to burn away. I'm not sure how long this has been going on or if it is from a leak that was fixed by the prior owner.

Given the pink color and location, I suspect it's transmission fluid. However I've looked at the transmission from all angles and cannot find a fresh leak anywhere. The output shaft seal doesn't appear to be wet. The body underside has this fluid all the way from about the middle of the transmission (but not on the transmission) to the gas tank.

The valve cover gasket was recently replaced due to an oil leak. Is it possible that I'm hallucinating the pinkish appearance and this is actually motor oil that's traveled down this far on the body? I welcome your thoughts. Thanks

 

Is this a 2wd truck?

 

Yes 2wd. Also 2.7L.

 

While the driveshaft does look dry, I can’t image it coming from anything other than the output seal leaking. It is clearly slinging off onto the underside

Also, without looking up the parts, it’s doubtful that you were looking at the output shaft seal; it’s most likely the dust boot you see
So, you can drop the driveshaft and pop the boot off and take a look, but if you are going that far you might as well just replace the damn seal

 

Looking at your images it is clearly a transmission output shaft seal leak. You can see where it is getting slung off to the body...
This doesn't mean you don't have a leak at the valve cover etc...

What you can do is get some degreaser, clean it well and then monitor it daily to see where it is coming from.

 

I scrubbed down the entire area this morning and will keep a close eye on it. My current hypothesis is that either it was from a previous leak that was fixed, or that it only leaks under certain conditions. Time may tell.

 

Let us know what happens.

 

It's been about three weeks and it looks like the leak is active. I'm assuming it is the output shaft seal as I originally suspected. Let me know if you have an alternative hypothesis. Thanks to everyone for weighing in.