[Thad House]

Originally Posted by DampRobot

Sounds like it's in the belts then. Is the gearbox in the middle? Is there any significant resistance when you turn the gearboxes by hand?

I edited my post after i saw yours. It does not happen when the belts are not attached, and its in the middle. But we still have no clue what would actually be popping on the belts, because we are looking and they are not riding up the pulleys. Maybe when the tension is added to the center, it does something odd to that center axle. The pop reverberates through the entire side, so its hard to tell exactly where it is coming from. And there is no significant resistance other then the gear reduction. the popping doesnt feel like a skip if you hold the wheel. its barely noticeable.