I just recently bought a slayer that had a 2.5 in it. I removed the 2.5 and put in a 3.3 with in 15 mins I completely destroyed the spur gear.. Any idea why this happened?
Most of the time when the spur gear strips it's from an improper mesh between the clutch bell and spur gear. To loose or to tight will strip the spur gear. Also, check the clutch bell bearings, when they fall apart it will strip the spur gear.
Also, check to make sure your engine mount isn't bent or warped. I thought mine was ok and it was an adjustment problem that I was chewing up spur gears. Turns out my engine mount was bent, ended up breaking entirely.