The gears are hardened steel!! The only flaw with Genesis Tranny is that it can slammed into reverse while the tranny is still rotating which could cause breakage of the reverse slider and subsequently the rest of the gears due to loose hardened broken slider parts inside tranny. I have locked out or removed reverse in both my Nemesis w/ third gear added and my Genesis trannies and had NO problems with them at all. But other than that this tranny is super strong. I wear out dog bones and cvd's before the tranny shows any sign of wear!!! You might want to consider useing the Nemesis tranny due to the larger out-put bearings and the "metal to metal" 4 disk brakes(far superior stopping power) for your larger and heavier custom truck, the cool part of Nemei tranny is you still add reverse and the third gear just by adding "bolt-in" parts!!!

Good luck with your build-up!!!

Post pics if you can!!!!!