Gear oil...
 

So, I've read a couple of write-ups and I've read what's in the manual...I've seen 75W-140, 75W-90 and the manual says 80W-90. I plan on using Royal Purple...what weight should I go with?

I've been running Royal Purple 75W-90 for a couple years now, no issues.

When i changed mine i went with 75W90 Valvoline Synthetic Gear Oil. I just followed these instructions: Project-JK.com - Jeep JK Wrangler Resource » Jeep JK Wrangler Maintenance Differential Fluid Change Write-Up

Easy enough..
Augi:beer:

75W-90 and 80W-90 are close enough to be interchangeable. Use it in the front; and in the rear if you don't tow a lot.
Use 75W-140 synthetic in the rear if you tow a lot.

That's what I did with eddies write up

Save yourself the money and just get dino fluid. RP is so friggan expensive any no real benefit. If you wheel at all, you should be checking/changing the fluid often and RP is expensive to do often.

After having my 4:88's installed I actually use Lucas 75-140 in front and rear. Do some towing,but not a huge ammount. No issues at all. I use RP 5w-30 in my engine without any issues at all.

Thanks, everybody!!

I found Amsoil at the show in Moab and after doing some research on there gear oil that is the route I will be taking. Recommended at 100,000 miles or 2 years, I would say thats pretty good.

I don't care about any oil manufacturers recommendation. You should be changing your gear oil often if you wheel. If you are a mall crawler, sure go for it. But proper maintenance and knowing what is going on with your rig is crucial. And if you aren't touching something for that long that should be a part of regular maintenance, well...best of luck to you.