The biggest weak point in the 02M & 02Q gearboxes is the 4th gear. There is a risk that at high torque the input shaft starts to vibrate and the shaft is pushed away from the opposite shafts, so that the gear pair of the 4th gear no longer meshes properly. Consequence: the 4th gear breaks off! Our solid shaft works as follows: By pressing a special steel core into the input shaft, the hollow shaft becomes a solid shaft and thus vibrations are reduced and the gears run more cleanly into each other. It should be noted that not every shaft is the same. If our core does not fit, the core can be welded on. Manufacturer Information about the manufacturer BAR-TEK BAR-TEK Motorsport GmbH Im Rauschen Auel 3, 51491 Overath-Brombach, Germany info@bar-tek.com