Input housing failure at the shaft and forward piston areas is common in high-torque 4L60, 4L60-E, 4L65-E and 4L70-E transmissions. Sonnax input housing forward sleeve kit 77733-52K is used in combination with a Sonnax overrun sleeve to greatly increase the maximum strength of the housing and prevent these failures.
Installation of an overrun sleeve — available with Sonnax input housing overrun sleeve kit 77733-51KA and Smart-Tech input housing kits — is a common durability upgrade in these units. Even with an overrun sleeve, though, a large portion of the input shaft and aluminum housing spline connection remains unsupported. Adding the Sonnax forward sleeve kit nearly doubles support in this area, making it a recommended component for all high torque capacity work/sport vehicles.