I've been using 85w140 in transfer case and diffs for about 40 years. Also in the gearbox on Series Rovers.
I used to use Drydene, but they got bought by Castrol and I don't have a source close to me, so I just use the house brand most of the time.
For the R380 I use Redline MT90.

 

Holy crap that's a GOOD deal!!!

 

Ha!! I just bought 27 of them and used coupon code: CC5OFF
Came out to $2.84/bottle with free shipping!!!

 

I buy that Lucas in the 5 . Works out to fair price, but^ is a good deal

 

For transfer case and differential oil (7 quarts), in town I have located:

-85/140 Taylor Petroleum Ultramar (not synthetic) 20 L pail that comes out to be $4.25/L

-75/90 synthetic - what I have now

I have also found:

-85/140 Lucas $3.99/qt (not synthetic) - the one I posted before

from:

Lucas Oil Part 10062 - SAE 85-140 HD Gear Oil - 4 Wheel Parts

I cannot seem to locate any 85/140 synthetic in Eastern Canada (where I live).

Suggestions? Is the Lucas too thick - do you just use it straight? Okay in our cold winters?

Also, I have read about limited slip additive - is this good to use?

Thanks!

 

My thoughts in BOLD.

 

85W140 is lighter weight when cold than 90W.
There are different kinds of limited slip diffs. If it's the kind that used discs you need additive or LS specific fluid. If it's a gear type you don't.

 

Does being in a warm climate affect which weight gear oil I should use? Are there any downfalls of using one over the other?

 

I love 85w140 in the diffs. Just recently started running it in the case and it's getting noise. Also leaking. I'm going to drain it, take a peek under the inspection plate and refill will 75w90 and see if it changes anything

 

I just started running royal purple a few months back, it is in my diffs, want to do the t case but broke off the drain think it is 75w/140?

In the real cold weather there was an instant a noticeable difference in resistance after I changed it out