4L60E Transmission Sonnax High Performance Pack Build Upgrade Package This Super High Quality Kit Contains Upgraded Parts Manufactured by Sonnax Don’t Risk throwing products from different manufacturers into the same tranny when there’s no guarantee they’re all going to work well together. Installing Sonnax parts designed to work together is the BEST and Safest way to upgrade your transmission and achieve the performance you want out of your rebuild. We have packages designed for Heavy-Duty pickup builds as well as performance builds starting at the most basic level 1 all the way up to level 3 which is for extreme performance. 4L60E-L1B (Level 1 Option B) Best parts for performance re-calibration and durability. Most Change in shift feel comes from the performance pack. Includes Performance Pack, Smartshell HD Reaction Sun Shell Kit, and upgraded Rear Stator Support Bushing 4L60E-L1B (Level 1 Option B) kit includes: Performance Pack: Sonnax Performance Pack HP-4L60E-01 combines innovative heavy duty/performance calibration for firmer shifts under load without sacrificing low-speed drivability. The precision components in this kit upgrade the 4L60-E for maximum performance and durability by recalibrating pressures, re-calibrating shift accumulation and including improved parts for areas that commonly wear. This kit is suitable for any heavy duty application and is a critical foundation for other upgrades when modifying the 4L60-E for high performance use. Shorter shifts which get progressively firmer with load Faster pressure increase and higher overall pressure for greater clutch/band holding power Three ultra-reliable, patented, billet pinless accumulator pistons Unique 1-2 accumulator spring combination for shifts with character Improved high RPM pressure Third accumulator valve gets the 2-3 right the first time, every time Consistent results, no guessing on calibration Prevents worn accumulators and separator plate Optional TCC on-off conversion prevents excess TCC pressure SmartShell HD Reaction Shell Kit: In GM 4L60, 4L60-E, 4L65-E and 4L70-E units, bulky aftermarket shells always fall short when splines continue to strip and the shells break under stress. A chronic problem with both OE and thicker aftermarket shells is failure of the rear planetary bearing. From daily jobs to extreme builds, the Sonnax SmartShell heavy-duty reaction shell kit 77749-02K is the only way to prevent shell failure AND protect the bearing. The SmartShell avoids the weight found in traditional, heavy-duty aftermarket shells thanks to a unique combination of improved design and manufacturing for a super strength shell that's only slightly bulkier than OE. To prevent thrust loads from overwhelming the captured planetary bearing, the SmartShell features a larger bearing and custom roller clutch race. These parts re-route thrust loads through the carrier, completely bypassing the delicate bearing. 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.