I have a 60" KK tiller. Run the hell out of it every year preparing fields for tree seedlings, minimum of two acres per field. Makes real nice smooth, even tilth of soil for planting seedlings.
Sometimes I will break ground with a heavy off set disc before tilling, sometimes I just hit the field with the KK tiller.... Depends on moisture of the soil, timing or just available time.
I run 00 grease in my side gear box and I think 85-140 gear oil in the top box. The reason for the 00 grease in the side box is after about two years oil started to weep from the box around the torque tube. KK recommended that, so I did it. No oil weeps and still works fine years later. I also added 'trash guards' to the torque tube to help keep woody stems and other tangling stuffs from wrapping around the tube and into the seal

A guy should dig that crud out when it accumulates....
I did have to replace a U-joint a little later that same season. Its a common u-joint and Napa has them on hand, Precision 334 u-joint.
I use too till gardens on top of tree farm usage, but not so many now. Like I said, I run the H-E double hockey sticks out of my kk tiller.