General chaincase oil no need to be picky but you could go synthetic. Some people use 80w90 gear oil I believe is the #'s that also is suposed to work. You're cat dealer will also have this along with any other snomobile place. To change it you need to first drain the oil(there is a plug inside the tunnel where the chaincase is), secoundly you could skip to a fill up or go and take the cover off to make shure everything is good(highly recomended). Make shure you fill it up after the inspection lol.
You're speedo may not be a quick fix since usualy the drive shaft bearing in the speedo adapter goes and shears off the key. The speedo not working is a hint that the bearing is going to explode sometime soon and should be looked @ real quick. Its not extremely hard to do if things go right
.
