Rocker Arm Shafts For 01-19 GM 6.6L Duramax XDPThe XDP Rocker Arm Shafts XD385 are specially designed to minimize the common oiling issues in the 2001 2019 GM 6. 6L Duramax engines. From the factory, the oil supply to the rocker arm is shut off as the valve is opened. This lack of lubrication can cause excessive wear on your valvetrain and premature failures, especially in high performance applications. The XDP Shafts feature revised oil grooves that align with the oil hole in the bushing so you