6L90 Performance Transmission Rebuild Kit - Level 4
Kit is designed with 45-tooth 4-5-6 clutch plates. CDT's Billet 4-5-6 clutch hub and intermediate shaft (CDT part number 104690-45) is included in this kit. The 4-5-6 clutch pack provides 45% more surface area than a stock clutch set up. The 3-5-R clutch pack offers 40% more clutch area than stock.
This performance transmission kit comes with printed instructions for all of the items in the kit except for the Sonnax items. For installation instructions for Sonnax items, click here.
6L90 CDT-BROC (4140 HTSR Billet Reinforced Output Carrier)
This part is designed for vehicles producing over 750 RWHP, Nitrous or Heavy Vehicles (including trucks, SUV's and CTS-V's).
It is a drop in part for easy installation.
4140 billet steel drive plate to strengthen the spline area.
The drive plate is milled and contoured to the planetary housing to eliminate any possible separation under a load.
CDT456L4/90 (4-5-6 CLUTCH KIT)
(8) Alto G3® Clutches
(9) Heat-Treated Steels (varying thicknesses)
(1) Stepped Apply Plate
(1) Wide Backing Plate
(1) Snap Ring
(2) Hi-Per Blue® Bonded Pistons
CDT456L4/90 offers 45% more clutch apply area than stock. G3® friction material is formulated to achieve minimal wear and maximize heat resistance. Our steels are heat-treated and cooled in air, producing a stable and consistent plate that resists warping and ensures smooth clutch operation. This process improves durability and promotes even wear when paired with premium friction materials. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance, with better fit and performance.
104690-45 (BILLET INTERMEDIATE SHAFT & 4-5-6 CLUTCH HUB)
One-piece 300M steel forging is heat-treated and shot-peened for maximum durability. This shaft doubles oil flow to the clutch pack for improved resistance to heat and longer clutch life. The hub is designed for use with 45-tooth clutch plates. This shaft is designed for use without OE dampner.
CDT35RL4/90 (3-5-R CLUTCH KIT)
(7) Alto G3® Clutches
(7) Heat-Treated Steels (varying thicknesses)
(1) Steel Plate
(1) Apply Ring
(1) Backing Plate
(1) Snap Ring
CDT35RL4/90 offers 40% more clutch apply area than stock. G3® friction material is formulated to achieve minimal wear and maximize heat resistance. Our steels are heat-treated and cooled in air, producing a stable and consistent plate that resists warping and ensures smooth clutch operation. This process improves durability and promotes even wear when paired with premium friction materials.
CDT26L4/90 (2-6 CLUTCH KIT)
(6) BorgWarner® High-Energy Clutches
(6) Steels
(1) Snap Ring
(1) Hi-Per Blue® Bonded Piston
High-energy friction material provides the proper friction coefficient, ensuring consistent shift quality and dependable durability. Designed with advanced fiber reinforcement and oil-holding porosity, it delivers stronger holding power, cooler operation, and longer clutch life. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.
CDT1234L4/90 (1-2-3-4 CLUTCH KIT)
(6) BorgWarner® High-Energy Clutches
(6) Steels
(1) Backing Plate
(1) Snap Ring
(1) Spiral Snap Ring
(1) Snap Ring Kit
(1) Hi-Per Blue® Bonded Piston
High-energy friction material provides the proper friction coefficient, ensuring consistent shift quality and dependable durability. Designed with advanced fiber reinforcement and oil-holding porosity, it delivers stronger holding power, cooler operation, and longer clutch life. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.
CDTLRL4/90 (LOW-REVERSE CLUTCH KIT)
(6) BorgWarner® High-Energy Clutches
(6) Steels
(1) Hi-Per Blue® Apply Piston
High-energy friction material provides the proper friction coefficient, ensuring consistent shift quality and dependable durability. Designed with advanced fiber reinforcement and oil-holding porosity, it delivers stronger holding power, cooler operation, and longer clutch life. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.
CDTVBPKL4/80-90 (VALVE BODY & PUMP KIT)
(2) Boost Valve Springs
(2) Clutch Regulator Valve Springs
(1) Center Support Seal Kit
(1) Pressure Regulator Valve Kit
(1) Line Pressure Booster Kit
(1) O-Ringed End Plug Kit
(1) Pump Slide Spring
The valve-body and pump modifications in our 6L90 Level 4 Performance Rebuild Kits are a carefully selected combination of TransGo and Sonnax components. We chose these brands because, through testing and experience, they deliver the best results for pressure control, shift quality, and long-term durability. Each part is designed to work together as a system, ensuring maximum performance and reliability. For this reason, we don’t recommend substituting or adding other components, as doing so can upset the hydraulic balance and reduce the effectiveness of the kit.
CDTMKL4/90 (MASTER KIT)
(1) High-performance overhaul kit engineered utilizing premium materials for racing.
(1) Bonded OE Valve Body Plate
(1) Bushing Kit (includes extension housing bushings)
(1) Pan Gasket
(1) Filter
(1) Oversized Pump Washer
We do not include welded hubs in the Kit. At the beginning of R&D on this transmission, we thought this area needed strengthening. However, in all the units that we've rebuilt, we've NEVER seen one broken. Therefore, we deemed it unnecessary. Also, we do not include a billet pump rotor because the factory pump rotor has proven itself reliable (we have never seen one broken,) unlike the 4L60E.
PLEASE NOTE: GM has a transmission that has the same outside dimensions as a 6L90 but uses one less clutch in all the clutch housings compared to a true 6L90. We call this transmission a 6L90LCC (less clutch capacity). Please refer to "Stock Clutch Capacity Chart" and "Length of Main Case Chart" on the "Transmission Specs" tab below to determine if you have a 6L90 or 6L90LCC. When ordering this part, please indicate in the Notes textbox above that you have a 6L90LCC. If you are unable to determine if you have a 6L90 or 6L90LCC, we will determine which transmission you have from the VIN.
Recommended Transmission Tools
- Transmission holding fixture
- Calipers
- Dial Indicator Set
- Bushing Drivers & Arbor Press for Bushing Installation (Bushings should only be replaced as needed)
- Sealing Ring Protector and Sizer
- Various Clutch Spring Compressors
- Output Carrier/Shaft Lifting Tool
- 1-2-3-4 & 3-5-R Clutch Housing Installer
- Large Snap-Ring Pliers
- Pump Alignment Tool
Misc. Transmission Information
Upgraded Parts: If you have an early pump cover (stator) that does not utilize anti-rotational tabs on the sealing rings or an early 1-2-3-4/3-5-R clutch housing that does not have the matrix stamp, you will need to install a factory-upgraded pump cover and clutch housing.
Transmission Tuning: Please understand that proper tuning of the TCM and ECM is mandatory. All 6L80/90’s are torque-based shifted units. The torque signal is calculated through the ECM. Therefore, transmission performance and longevity are directly dependent on the delivered torque signal that’s calculated in the ECM. If this is not done properly, you will experience premature transmission failure. We also do not recommend maxing out pressures or deleting torque management completely because it will cause seal failure and/or hard part breakage.
Flushing Cooler & Lines: We cannot stress enough the importance of flushing the transmission cooler(s) and lines, even if they are new. We recommend using a Hot Flush Machine Flush Machine or something comparable.
Auxiliary Cooler: You need to install a stacked plate auxiliary transmission cooler (not a tube and fin style cooler) rated for 25,000 GVW. The ideal operating temperature for this transmission is 180°or less. These transmissions tend to run very hot, so the cooler will lower the operating temperature and recovery time, which in turn will extend the life of your transmission.
