Thats what I use!

 

Redline is great oil, that being said dont waste your money.
You are better off using a cheap brand and changing it more often.
I use Wal-Mart brand, 85w-140 and change it once a year.
I made the mistake of using Mobil 1 the first year I had my truck, went wading, got water in the rear diff, almost cried as I drained out 3 month old $30's worth of gear oil.
Fixed the problem but still cannot get myself to spend a whole paycheck on gear oil when the truck came from the factory with dino lube anyway.

 

I've drained and filled more diffs tboxes and swivels than most of you "experts" could ever dream of, I've taken more gear oil baths than i'd like to remember. 85/90, 75/90, 85/140... it all feels the same IMO.
Unless there is some scientific proof other than opinions, the factory recommendations have worked just fine for decades. Failures occur when you push the limit of the component more than it's capable of. No magical weight of gear oil weight is is going to change that..
That being said.. do whatever you like, and take advice from whomever you like.

 

Very true, OEM spec is good for 98% of people out there.
I have personally found that the heavier oil makes my truck quieter and reduces gear lash.
That is my personal experience, your results may vary.

Just to share, my work van (Ford) comes with full syn 80w-90 from the factory, the change interval is whenever the gears go bad, just keep it full and run it until it blows.
One of my vans had over 200k on the factory fill gear oil, and those are HARD miles too, harder than a taxi.