Not trying to change subject, but servi rear ends were made to use with low horsepower, narrow wheels, and low speeds. Just a warning, servi rear ends only have a small C clamp retaining clip which fits in grove on axles inside gear differential. They have no outer bearing retainers at outside end of axle housing like more modern vehicles to keep,wheel and axle from leaving axle housing with larger motors, larger tires, and higher speeds.