Duramax Allison 1000 2000 2400 Main Intermediate Shaft. As the Duramax power level keeps going up, TCS Products has been proactive to add a billet main/intermediate shaft to our Allison 1000/2000 lineup. Shaft is machined from 300M billet steel. Stronger than the O.E.M. intermediate shaft. Features an added lubrication hole for the P-3 sun gear and pilot. CNC machined and precision ground. Shaft is heat treated for added strength and durability. The shaft through hole is gun drilled to provide a polished interior finish, eliminating internal stress risers.