I used Mobile DTE 26 in my 1999 Grasshopper w/G2 trans. I read somewhere that it's the same as G2 Grasshopper Oil. I'm not sure if it will work in your G1 trans. To change the fluid pull the hose off teh hydro tank and then find a low mounted hose and pull that one. I put down a cheap plastic drop cloth & drove the mower on it. It can be a messy job.