[T@BD]

I agree, in forward the internal planetary gears and sun gear are locked together in unison, and there isn't an opportunity for gears to catch on each other. I believe whatever happened caused the planetary set to shift over and try to engage reverse while the kart was moving forward.

My bet is the cable arrangement, movement of the swing arm pulling on the cable. Don't worry about warranty, I'm sending out a replacement sun gear and collar. The planetary and outer ring gear look fine so this should take care of it.

Although I've never seen a sheared sun gear before, usually when reverse gets inadvertently shifted while moving the planetary gearset grenades into a bunch of pieces and chews up the outer ring. Interesting, the higher speed may have saved the rest of the gearbox.

I'm wondering what the deal is with the seized collar. You're saying that it seems to have welded itself to the output shaft? That would have been friction related, most likely not related to the other issue. I could be wrong, but it sounds like there were two underlying problems.

Let me know when you receive the replacement items, I'd like to see a few quick pictures of the final assembly and cable routing just to make sure.