A thin, weak backing plate is the leading cause of 3-4 clutch distortion and burnup – a pervasive problem in listed GM transmissions. Even the thickest OE backing plate flexes during clutch apply, allowing heat to build up unevenly, causing problems in daily drivers and mid-level street/strip vehicles alike.
Other aftermarket solutions typically employ a thinner backing plate, and thinner steels which ultimately exacerbate the problem.
Sonnax heavy duty 3-4 clutch backing plate kit 74140-01K significantly reduces backing plate flex for increased 3-4 clutch durability. It features a significantly thicker and stiffer backing plate, used together with a thinner (yet stiffer) apply plate.
Designed for use with GM high energy clutch pack with seven .067" frictions and six .095" steels, this kit can be used to upgrade OE 700-R4 and 4L60-E five-friction or six-friction clutch packs to seven frictions, or to improve stock, seven-friction clutch packs in 4L65-E and 4L70-E units by reducing backing plate flex.
April 28, 2017
Topics: Rebuilding Tips Transmission GM 4L60-E Transmission 4L60 Transmission 4L70-E Transmission 4L65-E TransmissionRead Now
June 06, 2018
Topics: Shop Practices Transmission GM 4L70-E Transmission 4L60-E Transmission 4L65-E Transmission 4L60 TransmissionRead Now