Although I have run a metal spur gear on a Hot Bodies Truggy, I've never run one on any Mugen. My truggy squealed like a pig with the metal gear, but it beat no longer stripping the plastic spur gear, which happened on a regular basis.

Having owned the 2 ECO's and now this 7, I rarely (if ever) feel the need to replace the plastic spur gear. This also applies to a lot of guys running Mugen. Some of which used to run Losi requiring a full stock of plastic spur gears as they were always stripping them. None of us have stripped the plastic ECO spur gear.

I have to admit, the thought crossed my mind to try the 7 metal spur gear with 7 diff case. Actually had the diff built up and in my parts box until someone offered to buy it from me. So, I never had a chance to try it.

Could be a tuning aid as the metal spur gear would offer a little more of the "flywheel" affect over the plastic gear.

Lastly, as far as wear, my HB truggy metal spur gear actually showed greater wear than a plastic gear. Also the thinner profile would wear the wider pinion unevenly.

That's just my experiences.

First priority is to finish races, second noise and last gear wear. If Mugen's plastic spur gears never strip and the wear is more even, I'll stay with the plastic to reduce some noise.

Either way is fine. Just personal preference. Although I would like to run all 7 diff components, I'm fine running the 6 diff case in the center.

Jim