What separates GearStar from most other transmission building companies is its custom-built transmission dyno. It’s able to simulate the loads and conditions transmissions are subjected to during normal operation. At its heart is a Chevrolet 4.3L V-6. The transmission is bolted to a large steel flange that’s fastened to the dyno. It accommodates most any common bellhousing bolt pattern. By connecting the transmission’s output shaft to an 800-pound flywheel, it replicates the loads seen when accelerating a typically-sized vehicle fitted with 3.73 gears.