Sonnax has introduced a new input housing forward sleeve kit (part no. 77733-52K), which the company says can increase input housing torque capacity and maintain OE forward piston apply area in GM 4L60, 4L60-E, 4L65-E and 4L70-E transmissions.
Sonnax suggests using it combination with a Sonnax overrun sleeve to greatly increase the maximum strength of the housing and prevent failures. This kit also requires a compatible overrun piston.