Question: are there different size pto shafts?
Answer: On some machines the shaft size was an option as the standard changed from 1-1/8 to 1-3/8. The popular Ford N-series tractors were equipped with the 1-1/8 inch PTO shaft. Because it has the same rotation speed and direction, this shaft size can usually be converted to 1-3/8 with a slip-on adapter.