540 6 spline and 1000 rpm 21 spline is ASAE standard across all makes. That don't apply to a mid pto like Kubota has, diferent animal.Standard PTO fro all major brand tractors is 540 RPM. I've never heard of 640 unless that calculates to what economy PTO is and I don't think it does.
You are correct Mr.Workinonit. I don't know how I got the 640 into memory. 540 is the norm.Standard PTO fro all major brand tractors is 540 RPM. I've never heard of 640 unless that calculates to what economy PTO is and I don't think it does.