there is another durango he runs a reedy 75/27. And most others are running sc10's with the same internal gear ratio. Running d4's and reedys as well. D4 has plenty of torque without the 12.5 rotor and the reedy Mach 2 comes standard with a 12.5 rotor. So i know my gearing isn't far off. As to why I tested the stock rotor and the 12.5 ht rotor. I have ran a handful of 17.5s over the years and I really like viper products. The r be esc is very smooth and stays cool and the xpert servo I have in my truck is fast and strong. I never picked up one of the old orange/red 17.5's as I was told they just wernt the strongest motors. But when I saw they had released a BE 17.5 with option to use different rotors I could not wait to finally pair up a viper motor to the rest of the package. I'm not going to give up yet. I Orderd new idler gears and a new layshaft set, a new gearbox and a fresh 78t spur. Orderd a new bfast ball diff and a new ball diff ring gear. I dought I need any of it but I want to fully give this motor every opportunity to shine. I'm going to replace the large bearings on the diff and rebuild the idler gear bearings and inspect the motor bearings as well. Pull all the wheel bearings and clean the cvds. Going to start with 78/23-24 and see where That gets me.