In my post I suggested looking in the fill hole, (top of oil), and the drain hole, (bottom of oil).
The OP has already driven his Jeep.
Oil floats on water.
Oil "mixes" very easily with water in a gear box. The oil becomes milky.

 

Doesn't hurt to check the oil regardless of water crossings.

First oil change with the JK, decided to do the diffs just for the hell of it, and glad I did. No water crossings. No mud. Just dry trails and lots of city driving.

This is what came out of the front -

 

Looks like you were brewing Cappuccino. Props for finding a second use.

 

Ronjenx is 100% correct. Pull the fill plug, if it has water in it you will see that it is over full. If you still can't tell then pull the drain plug. The 1st little bit will likely be water if the rig was sitting for a good amount of time. If it comes out as clean oil then you know you are fine.

And when all else fails just change it for good measures.

 

A hot diff will see a large volume change in the air inside it when it goes into cold water, this can suck water past the seals even with good extended breathers. Easy job to change the oil. Just make sure if you are running aftermarket lockers and diff covers that you do not overfill. If you are unsure of how much oil to use with an aftermarket cover just measure how much comes out

 

I just got around to checking the diff fluid today - I opened the front diff upper fill hole and - surprise!- a whole bunch of oil came pouring out. Well over a cup of 'oil' maybe almost 2 cups. it looked like chocolate milk. Not good - that extra volume must have come from water. So I changed both front and rear - they both looked the same. I guess I must have gotten a good amount of water in there. The jeep only has 20k miles on it, but it is an '08 so probably a good idea to check on the oil anyways.
wade

 

Dumb suggestion, for those of us who don't have the time to change our own oil/or whose dealers change it for free (gotta love the Jeep dealer in Saco Maine!)

Could someone post a couple pictures of how to check/drain/refill the diff fluid for say a 2012 JK with Dana 30 front and Dana 44 rear?

Matthew

 

From Jeep's blog:
"As an example, a 2010 Trail Rated® Jeep Wrangler’s maximum water depth is 30 inches at speeds under 5 mph, ..."

Jeep® Off-Roading 101: Water and Mud | Jeep

That said, if you have a 4" lift your breather hose WILL pop off during full extension. You need to do a breather tube extension at minimum. Raising the differentials, transmission and transfer case breathers is fairly cheap and easy. But no matter what you do, check fluids often.

Great write-ups here:
https://www.jk-forum.com/forums/jk-w...ite-up-105002/
https://www.jk-forum.com/forums/jk-w...al-2dr-246787/
https://www.jk-forum.com/forums/jk-w...d-pics-255587/

 

Writeups --> Index --> Maintenance & Operation

Super quick and easy. There is a fill plug at the middle of the diff cover, and a drain plug down on the back side of the diff housing behind the cover.

 

That's really how easy it is!