In regards to choosing what type of transmission i stand by dog gear shifters and more specifically the andy mark ones. My team ran with the andy mark 2 speed found here:
http://andymark.biz/am-0076.html
We started using them on a prototype chassis before the season and all we had to do to them was put some white grease on them. They are built with 4 mounting holes on both the top and the bottom. We did take them apart a few times to change the spacing on the output gears for the chain, and when we did that, I was very happy with how easy they were to work with. They are a bit expensive, but i feel that they are worth every penny. It's American made too, can't beat that, haha. But really, Andy Baker and Mark Koors know what they are doing and they make great stuff.
If you guys do not choose to use them for this season i would highly suggest that you walk around at comp and look for robots that are running them, and ask them what they think about the transmissions.
- Hope this helps