Yes Lou has the molded ones, we have had a pushing contest and my D8 has the upper hand. My pads cut into the dirt rather than float on the top. I would dig a deep hole very fast if I ran up agaist something the D8 could not push. Also the motor I use are 400 oz in per side on 18 volts 25 rpm. Nothing slows them down ! ! !
http://servocity.com/html/dayton_gear_motors__12v_.html