Here are some pictures of the tranny I modified for the brushless revo. I converted the revo 2 speed to a single speed locked in 2nd gear using an adapter plate I bought from Oomp(one of the guys over at traxxas forum).
Single speed adapter plate:
It was designed for the plastic 2nd gear so I have to dremel the RRP 2nd gear to make it fit.
I also drilled the shaft to 2.5mm so I can use a bigger pin(stub axle pin) for added strength:
Side by side with stock RRP:
