This may be known issue but one of my summer jobs was to check an top my transfer case, it leaks.

Symptoms

One thing I noticed was a clunk on shifting every now and then
The new front driveshaft seemed to have some rotational play

Leveled the Disco
Pulled my Filler plug - serpentine belt tool work great for that
My Transfer case was low it took about 11 oz of fluid to top, which to me is lot, but it is about 20 % of capacity.

Post top my front drive shaft was tight a no rotation movement at all.

I went for a 20 mile drive hi-way 65 mph and city no clunks no "rough" shifts, mix of flat and up hill/down hill
After that into a construction site with some ugly hardened mud ruts, went through hi low cdl lock in both no issues for 15 - 20 minutes

This is a bit odd to me as I would not have expected the top to tighten things up , but then I know very little about transfer cases.

But my take is make sure that thing is topped up, and if you have a small leak you may be losing more than you expect

 

I'm surprised it never got hot?

 

@Motorhead1 oddly no it worked beautifully, but I am going to do a complete drain next change. Not mention check it as part of a post trip maintenance.

 

Only some transfer cases have a temp sensor, tied to the transmission oil lamp. The sensor is on the driver side of the case, parallel to the ground

 

In case you don't have a temp sensor on the TC, there sits 14x1.5 bolt in that hole. I removed it and installed a temp sender. It still needs to be wired to my aftermarket sensor box.

Also, I had a leak on the TC. The cause was melted venting tubing. After fixing the tubing no more leaks. While at it, I replaced the TC oil. A 12V suction pump from ebay for $18 does the job of pumping up the fresh oil quickly (works also great on differentials, transmission and sucking out the oil from the steering fluid tank on both sides of the baffle). I installed a new drain plug with a neodymium magnet (Bearmach, ebay), which should collect more metal debris since it is 10 times stronger (measured with scales) than the original one.

 

Brilliant, on using the belt tool to remove plug. Have one, but never crossed my mind using it. Thanks, for passing info along.

Three out of the four Dll's l've bought were close to empty. Seems like no one checks this fluid level.

Brian.