John Deere year 2000 Model 4100 front hub/wheel lock up diagnose fix?

[Tubecat]

Hi folks, I was brush hogging the other day and my 4100 compact tractor front left wheel locked up for a bit, then would move freely and lock up and was able to slowly crawl it back to the shop. It looks like gear oil was leaking between the upper and lower section of the hub/axle area. I drained the gear oil and removed the upper 4 bolts and thought the lower section would drop down but it didn't. its hard to see in the picture but looks like there is a gap between the upper and lower sections and that there is a seal or shim that is broken or out of place.

Any idea what is wrong?
Any idea on how to remove the lower section? (do i need to remove the front of the hub or something?)

Thanks for any input you can provide.