I always thought that the whole idea behind swapping out the motors was to throw the wheels harder for rock crawling.
EDIT
I put a red ZZ motor on my Tri-Cell, but it also kills tha batts faster.
END EDIT
I've only seem a couple of references to the additional gear mod for the steering, but I haven't seen detailed instructions for it.
(If I find em, I'll post a link and will for sure be attempting it myself!!)
I noticed the additional battery drain when running upgraded steering motors too, and addressed it by adding an entire second battery pack from another MT when I built
Project: XL1 .
I wired the second battery pack in parallel to double the capacity (running time), as opposed to the more common series wiring that gives hellacious speed.