2004 Sportsman 500 front hub capacity?

Even though I’ve posted a couple of previous questions, I’m still a newbie.
My wife’s early 2004 (new to her last summer) is not engaging the left front hub lately. I drained the fluid from both, pulled the caps and cleaned the inside as instructed. Fluid was really dark. I could only get about 1oz in each side before it began running out the fill hole when rotated to about 3:30. Shouldn’t they take 4 or 5 oz each? Any ideas?

Also, every time I try to search a topic my results come back with nothing found comment. What might I be doing wrong?