I remember reading it's important to change trans. fluid and the filter at recommended intervals. My grader being an 86 may have been early enough to come with ATF from the factory (apparently caused slipping) but it mentions in the manual it should be changed 10W trans. fluid. I topped the fluid up a little but should just drain it and replace with new. I'm sure it has been changed because it has a NAPA filter but who knows how many hours ago and exactly what fluid was used. Maybe mixing with the top off oil contributed to the slipping?? AFD Petroleum as well as a new Petro Canada lubricants facility are both 10 minutes from me and have TO4 spec oil. The Petro Canada might only be a wholesale warehouse but I bought the top off oil at AFD. If I recall it was about $127/barrel which I thought wasn't too bad at the time. Who knows how much it has gone up now. Would be nice if a fluid change improves the issue.