Bill recently introduced the DTT billet drum, engineered to prevent uneven wear during the apply cycle of the piston. Notice the two slots machined in the center of the DTT drum (arrow). The OEM cast-iron drum has a single slot, which causes the piston to wear unevenly. The DTT billet drum also increases the surface area by 67 percent. With the OEM drum and the DTT billet piston, you can upgrade to a five-clutch pack. This new drum also enables Bill to change the OE factory friction clutches from four to six. This, combined with the higher-pressure valvebodies, increases the holding capacity by more than 2.5 times over that provided by the OEM system.