What year?
The drive unit will drop out the bottom after you remove the drive motor and remove 5 hex bolts. Once removed, you need to remove the 70 ball bearings that are trapped between the radial rings. It's not easy. once you remove the plug (has grease fitting on it) the **** will roll out. You must support the unit sidways, and let the **** drop out. Sometimes, the rings have shifted, and block the **** from falling out. Then, you need a die grinder to cut away at the rings until the **** fall out. Once these are out, the top ring slides off the main piece, and you can change the rings. Offset the gaps on install. You need to carefully install the **** without the rings falling out of place. Count them exactly at 70. Good luck!

by "bullring" I believe you are referring to the drive unit radial bearing. am I right?