There are 4 Axels: Old and New style Snow Trac, Trac Master, and Snow Master. They are interchangeable from right to left, but not from one machine to another. They are soft iron, and if the spline gets loose or develops any play one has to replace the shaft and the gear or drum or hub riding on it. Using an old brake with a new shaft will usually result in the new shaft deteriorating quite rapidly. Generally only the outer end where the Brass sprockets for the track are gave trouble. If you choose to have them made you have to go to a Gear & Spline specialty shop, not just a regular machine shop. Even some of the better equipped machine shops send their gear and spline work out to specialists. Having them heat treated would not be a bad idea. The last ones I had made cost about 600$ ea. That was some years ago. I found lots of worn out shafts at Twin Pines Equipment on the east coast, at both dealers in Alaska, and in the collection of parts from Northwest Tell in Whitehorse. It was a weak area in the original design. The final attempts to correct this was to have a 2 piece clamp on hub at the outer end. This did seem to work but only shows up on the very last machines built. As of serial number aprox 1600 this had Not been corrected.