Well I am glad to hear that I am not the only one to think this is strange to have the oil level 3/4 inch below the hole, never heard of such a thing.

 

I agree that the hole is in the wrong place as every diff. I've ever dealt with was filled until it runs out the hole. But I'm not the designer, so I have no clue why it is this way. All I can tell you is that if you fill the lube up to the hole, it will either:

a) blow out an axle seal (if your diff. is sealed up with the accordian thing) when it gets hot and over-pressured, or
b) blow out the breather tube when hot

Whether a or b, it will blow out until the level gets back to about 1" below the hole.

I used to keep filling them up, thinking there was some problem. But after everytime I ride FAST, my diff. breather tubes are dripping (all over my trailer), and when I get her back home and check, the levels are back to spec (1" below hole). So now I just make sure there is enough in there and don't worry too much about it anymore.

 

My wife's Cat was leaking 'something' on our trailer after going out riding the first few times. We figured we'd have the dealer look at it when we took them back for their first oil change and check up. Then all of a sudden it quit leaking. We never could find where it was coming from, but now it's gone. I wonder if this diff thing could have been the problem. Somewhere around 150 to 200 miles it quit leaking and we have almost 300 miles on them now. We checked the engine oil several times and that wasn't it.