I'm getting ready to swap diff fluid in both front and rear and was able to find the OEM reccomended capacities for both. However, I have ARB diff covers on, and the fill port is on the very top, so filling until is spills won't quite work, and it has a dipstick, albeit with no markings. I've done some searching around, and have heard everything from the ARB"s require a bit more fluid than OE, to they require less, to FITFO. I was wondering if anyone else has ARB diff covers and had suggestions for how much I should put in there. I've also heard that if I do put in too much, it'll just leak from the rebreather and be messy until it's level. Im not quite sure what the rebreather is though. Is that bad/ will it mess things up, or should I "when it doubt, fill it up and clean the mess later". Any help is appreciated in advance

2017 JKU Rubicon 3.6L 6 SPD Manual

 

I think all of us with aftermarket diff covers have this issue. From what I’ve learned, our diffs are splash lubricated. Meaning that the bottom half of the gears sit in the fluid and the gears splash the fluid around and lubricate everything else. So, I typically fill mine about half way up and use my fingers as a dipstick to determine if the fluid feels like it’s about half way up the axle tube. It’s a very precise science. This has seemed to work well for me.