4L80 Heavy Duty 1997-Up Intermediate Shaft. The 4L80 intermediate shaft is a 100% “drop-in” product made from 300 Maraging steel. Designed for high horsepower pro-street and off-road applications. For added strength and durability, the shaft is made without lubrication holes. Combine this shaft with the TCS 4L80 billet input shaft Part # 279600made from300M steel. The input shaft is stronger than the OEM shaft and is a necessary component for high horsepower pro-street and off-road applications.