I like to know if there's an existing gearbox, that will work with the Speed 900's? Or do they have to be custom made?

The reason is that I have just tested Mr Pink's pushing power. I put weights in a box (over 13.6KG) If you have seen the Leeds event video were when Pink push a robot it's slow, not fast and brutal.

You thought that 20T to 90T would be quick and powerful. I don't know why it's doing this but If I put a gearbox on the 900's, it may give a better performance on pushing power for Mr Purple.