That Valvoline will be a good choice, so would Wal-Mart brand, or Traveller from Tractor Supply.
No need to change it after you go wading, just check it for water ingress after you get home.
No water, keep going.
If you want to change it thats fine, I just dont want anybody to be fooled into thinking they need to change it every 6 month and spend the rent check on gear oil.
The DII came with full syn gear oil from the factory, LR says to change it at the first 30,000 miles and then every 60,000 there after.
The DI came with dino lube, 30k intervals for the life of the truck.
They both came with 80w-90.

 

all of this talk for this..
Lucas Oil/1 qt. 85W-140 high performance heavy duty gear oil its 8.99 a quart. buy it use it replace it. Sorry I mean with all the little things that our trucks need and demand form us a 4 page discussion over gear oil???? This stuff is cheap its good who cares if you change it once a year, once every 6 months. Its cheap. From the RAVE: fill for front and rear axle from dry is 3.6 pints. There are 2 pints per quart. sooo for 40 bucks you get to change out both diffs with extra. C'mon folks we fill with premium gas only at and average price of 3.82 a gal.. who cares about 40 bucks in gear lube. Changing twice a year is less than filling up the truck with gasoline, once.

 

^ well said

 

To check for water ingress do you let it sit for a while to seperate and then pull the drain plug a little and see if water comes out?

 

No, pull the fill plug, does milky goo start coming out?
No?
Stick your finger in the hole and check the fluid level, does the gear oil look like gear oil?
Yes?
You're fine.
It does not have to be clean, it can be black, just no water.
It takes days of sitting for oil and water to separate.

 

$9.00/qt is a rip off, $3.00/qt is what I pay, you need 7qts for all 3 diffs.
I buy 2 gals, less than $30.

Your point is well taken though.