This six speed overdrive builders kit is perfect when starting from scratch or when you want to use your own transmission housing and do not want to re-use any of your gears or shafts. This kit contains all parts -- includes main shaft with four gears, one-piece countershaft with three gears and sixth gear, shift drum, two shift forks, an improved shift drum detent system, and all other parts needed for the conversion. The billet trap door, which is fully machined from 6060T6 billet aluminum, is complete with bearings.