Combines N 6 hydraulic drive splines

I had the same problem several years ago. Most of the damage was to the coupling and not to the spline on the pump shaft. I purchased a new coupling and put it on with medium strength locktite. Have run it several years without any problems. I believe the dealer said I could order a new pump shaft if I need to. The spline is the same as used on coupling for front mounted hydraulic pumps on older Ford tractors with loaders; but you would have to split it and weld on the bolt tabs to tighten it to the pump shaft. Hope this information helps. Have you had any problems with the rubber connectors breaking that fasten the coupling to the PTO shaftIJ Mine broke before the coupling broke. years ago. Wonder how frequently this happensIJ

Main reason rubbers have ever failed is main drive or chopper belt got into them. Other very rare reason is misaligned pump. Pump can become out of line from main drive belt wraping around pulley which can put extreme pressure between bell and pulley. That pressure can bend plate that bell mounts to. I have also found once that spline was welded off center from rubber mount holes which ate up rubbers yearly.