Mountfield SP460 Rear Roller?

The rear roller has worn through the gearbox drive shaft. When I came to fit the new shaft it looks like the roller frame is wider than the shaft so if I fit the new shaft it looks like the same failure is going to happen again. As anyone come across this failure before as the mower is redundant without I can resolve the rear roller problem and the parts cost are expensive to get it wrong.

John
July 2010