I've ran both the PSI 4 gear gearbox and the original cam gear/extra idler system and the 4gear is better. With the extra idler, the motor sits farther forward (like the 22) With the 4 gear it was simply more planted on dirt. I haven't tried the extra idler on carpet but I might in a few weeks when I switch everything back for carpet (running 2 dirt race tomorrow and on the weekend) so I cannot say which is better on carpet. The 4 gear is a much cleaner look (but not as pimp as the one on page 2
) and much easyer to set the gear mesh. Contrary to popular belief, my mid motor xxx-cr is alot better then rear motor in low grip. If you run really low grip, the extra idler might work if you put the xfactory fly wheel on for even more forward weight transfer but you might loose all forward traction.