I purchased a 6x6 RC 4wd Worminator last August, and have worked on the gearing problems to the point where I think I may have found a couple of good solutions. No more lack of power, no more screaming gears, and I'm running a brushed 540 motor with a NiMH 7 cell battery that lasts 30+ minutes. 25:1 gearing in diffs. Speed up to 180 FPM in one setup, up to 100 FPM in the other. No home made parts, just some simple mods to available stuff.
Since I'm a newbie, I promise I will fumble with all the acronyms and stuff you guys use, but bear with me while I learn. Some photos will follow in the near future, but my work has me on travel a lot....