I am using BelRay Gear Saver SAE 85 with my Dirt Digger and stronger springs with excellent results. Stopped my creeping issue. Seemed like all the oil was flinging out of the clutch pack causing friction and therefore the creeping.
What kind of Gear Oil you running? Stock or aftermarket clutch? I had that same issue with my dirt digger running certain non- synthetic oils. I starting usiing full synthetic gear oil and it never did it again.