Leaking (sealed) U-joint

I was under my truck today greasing the non-sealed U-joints on the front axle when I noticed the "sealed" U-joint on the rear axle at the transmission is seeping a bit. You can see there's some wetness and even a little bit of grease is coming out at the top of the 1st photo.

The other two sealed units, at the carrier bearing and rear diff, are bone-dry without a hint of wetness (2nd photo). Should I be concerned? About 13,000 miles on the truck (2018 DCSB OR MT).

 

Normal.

They really grease them when assembling them. They heat up a bit when in use and the grease swells a bit. The grease is pushed out a small amount.

Good on you keeping an eye on things.

 

You should be ok and will know when your u joint is going out. That looks completely normal.