4L60E Transmission Sonnax High Performance Build Upgrade Package This Super High Quality Kit Contains Upgraded Parts Manufactured by Sonnax 4L60E-L1A (Level 1 Option A) Upgrades for performance recalibration and durability, no trans removal required Most change in feel comes from the servos. Choose your 2nd gear servo either the super hold 77911-03K or “Corvette Ratio” 77701-04K. Servo pin pictured is NOT included in this kit. Choose the Line pressure booster Kit (4L60E-LB1, 4L60E-L2) Includes upgraded Rear Stator Support Bushing 4L60E-L1A (Level 1 Option A) kit includes: Line Pressure Booster Kit: This kit comes with the Pressure Booster Kit; You will need to know if you have an early or late design pump in order to supply you with the right booster valve kit. This kit comes with the Early Style boost kit if you have the late style please see our other listing. The way to tell which it is you have is by the pump cover on the late one there is a cut-out in on section, where as in the early design it is just continuous See 2nd and 3rd images for reference in identifying the early and late pump covers. Sonnax hydraulic line pressure booster kits contain stronger pressure regulator springs and large ratio boost valves designed to work together to provide progressive pressure increases as driving conditions become more demanding. Our pressure regulator springs are approximately 10% stronger than OE and more conservative in impact than other aftermarket kit springs. Large ratio boost valves provide higher pressure incrementally and when it is needed the most. The combination of these springs and valves in a Sonnax kit gives you the best of both worlds: a modest pressure increase at the low end, with a high-end pressure that is equal to or greater than that of other aftermarket kit springs. Rear Stator Support Bushing: The original GM 4L60, 4L60-E, 4L65-E, 4L70-E rear stator bushing comes in narrow and wide versions in both common bronze and harder aluminum type materials. All versions commonly fail or wear out prematurely. Available aftermarket replacements typically have a poor quality fit and are also known to wear. For maximum durability Sonnax offers rear stator support bushing 77002BT-01, a better fitting and extremely wear-resistant, PTFE-lined bushing to stop future wear in its tracks. The Sonnax bushing is the best option for supporting the 20 lb. input housing and for improving the reliability of these common units. 4th Gear Super Hold Servo: 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. Patented dual-piston design with 40% more apply delivers greater holding power D-ring seals prevent pressure loss 2nd Gear Superhold or Corvette Servo: This is a choice between the two 2nd gear styles of servos for which performance option is best for you. We offer two options for your 2nd gear servo this kit comes with Corvette Servo- Sonnax 2nd gear "Corvette" ratio servo kit 77701-04K provides increased apply area resulting in improved holding power for firmer 1-2 and 3-4 shifts. The servo piston features D-rings in place of the OE seal rings for improved sealing during apply and release. This kit is compatible with Sonnax 4th gear Super Hold dual servo kit 77767K. Upgrade used for high performance or heavy-duty towing applications. Improved D-ring sealing configuration. If you want the Super hold Servo in place of the Corvette please see our other listing.