ABout ST4 Drums & Spline Shafts:
These generally need to be replaced in pairs. I Know this isn't Good News! Both the splined Axel shaft and the Brake Drum used on 2 Belt Snow Trac's and 4 Belt Trac Masters are made of soft material. If you put a new drum on an old spline shaft or 'Vice-Versa', you will end doing it over again. After visiting every dealer in North America and Alaska, as well as buying out the Canadian Phone Company what I found was there is an inherent weakness in this spline arraingement. All of the Dealers had piles of defective shafts. I tried it and found out myself the hard way. Later I was having shafts made and took them to an outfit that would heat treat them to make them harder. Of the dozen Snow Trac's, and 4 Trac Masters I've owned, and perhaps another 25% of the hundred or so other ST4's I've looked at and worked on, all had spline shaft problems. I started saving the old drums in anticipation of having an Insert made, sort of like a Helicoil only Spline to Spline, then having it heat treated. The very last machines produced had a special 2 piece clamping fitting made that carried the front sprockets. At this point they(AKTIV) had already moved the brake drums to the interior of the engine compartment. This "Fix" seems to have worked. In one case in alaska a frustrated owner had welded the shafts solid to the drums. Unfortunately his "Permanent Fix" prevented him from keeping the brakes operational and he soon wrecked the machine. There are several different front Axel shafts, the left and the right of all models are the same, but the overall length and bevels and splines differ from one run of production to another. When reassembling they need to be a real tight fit with absolutely no free play.