Sonnax 4th gear super hold dual servo kit 77767K features 40% more apply surface area for greater holding power in GM 4L60, 4L60-E, 4L65-E and 4L70-E units. Vehicles with these transmissions often exhibit poor 3-4 shift quality and experience band failure in performance applications. Combine this servo kit with Sonnax 2nd gear servo 77911-03K for unmatched holding power and shift performance that's an easy in-vehicle install.