About 4 months ago I purchase and installed the 285-251 spindle for a JD Z925A. It failed this month. Failure diagnosis have been completed by me. Upper pulley mount completely stripped its double hex mount. Completely stripped the spindle shaft too. Part of the part problem was the way the spindle was assembled as the lower spacer was too narrow allowing the spindle shaft to rub on the spindle housing. Also while rebuilding the spindle also found that they use different lower seal.
Upon removal found lower bearing rusting. Remove the bearing to find out they use a sealed bearing on a greaseable spindle. After removing the inner seal of the 6205-2RS bearing install it along with an OEM grease seal. Probably the upper bearing is the same but didn't check it as it feels okay.
Even using the lower spacer original spacer from a worn out OEM spindle I found that spindle housing was still being rubbed by the spindle shaft even through the spacer was thicker. A die grinder with carbide file resolved the issue of the rubbing.
At least Stens honored the one year warranty on the spindle so the customer is not out the $145 nor am I out the cost of the spindle assembly.
I am hoping that the issue I found has been already resolved, only time will tell.