Thanks guys, I haven't had a chance to cut again yet, but I'll let you know what I find. I assume the gearbox probably takes 90W oil. I've noticed they are selling 140W oil now at the auto parts places.
Yes. The gear box takes 90w oil. The gear box on my 6' mowing deck also gets rather warm to the touch and a bush hog that I use occasionally does the same. You are all set.