1970-1979 Ski-Doo Snowmobiles Service Manual, Page 156Get this manual
REAR SUSPENSION AND TRACK
6Disengage sprocket teeth from track, pull drive axle towards end bearing side of frame and remove drive axle assembly (Figure 13)Do not lose spacer or shim (if so equipped) located between bearing and lower chain case sprocket
bInstall chaincase as outlined in Chapter SevencPerform Track Tension Adjustment as outlined in Chapter TwoInspection