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6L90 Performance Transmission Rebuild Kit - Level 2

Rated up to 600 RWHP, HP ratings are contingent on numerous factors, such as tune, vehicle weight, power adder, use, etc. | Detailed Instructions Included | FREE UPS Ground to the contiguous United States (lower 48)

Kit is designed with stock dimension 36-tooth 4-5-6 clutch plates and will work with the OE intermediate 4-5-6 clutch hub. CDT's Billet 4-5-6 clutch hub and intermediate shaft (CDT part number 104690-36) is not included in this kit. The 4-5-6 clutch pack provides 14% more surface area than a stock clutch set up. The 3-5-R clutch pack offers 20% more clutch area than stock.
Availability: In stock
In stock items ship within 1-2 business days.
Picture for representation purposes only. Actual contents may vary as we continue to develop our products.

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. If you would prefer printed instructions please click the checkbox below:

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$1,495.00
SKU: CDTL2PK/90-P

CDT456L2/90 (4-5-6 CLUTCH KIT)

8 Borg Warner® Clutches
7 Lindered Steel Plates 
1 Apply Plate
1 Backing Plate
1 Snap Ring
2 Bonded Pistons

CDT456L2/90 offers 17% more clutch apply area than stock. Lindered is a chemical and heat treatment process that hardens the steel, which results in less wear.


CDT35RL2/90 (3-5-R CLUTCH KIT)
6 Borg Warner® High Energy Clutches
7 Kolene® Steels (varying thickness)
1 Backing Plate
1 Snap Ring

CDT35RL2/90 offers 25% more clutch apply area than stock. High Energy material maintains consistent frictional behavior and tolerates extreme thermal stress applications. Kolene steels provide a surface treatment that enhances wear & fatigue resistance.

CDT26L2/90 (2-6 CLUTCH KIT)
6 Borg Warner® Clutches
6 Steels
1 Snap Ring
1 Hi-Per Blue® Bonded Piston

Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.

CDT1234L2/90 (1-2-3-4 CLUTCH KIT)

6 High Energy® Clutches
6 Steels
1 Snap Ring
1 Spiral Snap Ring
1 Snap Ring Kit
1 Hi-Per Blue® Bonded Piston

High Energy material maintains consistent frictional behavior and tolerates extreme thermal stress applications. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.


CDTLRL2/90 (LOW-REVERSE CLUTCH KIT)
6 High Energy® Clutches
6 Steels
1 Hi-Per Blue® Bonded Piston

High Energy material maintains consistent frictional behavior and tolerates extreme thermal stress applications. Hi-Per Blue® Pistons are manufactured with upgraded High Performance Blue AEM material for superior thermal and chemical resistance with better fit and performance.


CDTVBPKL2/80-90 (VALVE BODY & PUMP KIT)
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


CDTMKL2/90 (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

 

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.

 We do not include welded hubs in Kit. In the beginning of R&D on this transmission we thought this area needing 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.

transmission specs worksheet

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.

Transmission Rebuild Kit Warranty

Limited Warranty Statement

Circle D's Transmission Rebuild Kits carry a 1 year, parts-only warranty, exclusively against manufacturer’s defects. The warranty period begins at the date of purchase. There is no warranty under the conditions listed below. This includes, but is not limited to:

  • Improperly Stored
  • Improperly Installed
  • Improperly Tuned (EMC or TCM)
  • Misapplication
  • Altered, either by Owner or Their Technician
  • Torque Converter Failure
  • Inadequate Flushing of Transmission Cooler
  • Improper Fluid Level
  • Water/Engine Coolant in Transmission
  • Excessive Power
  • Accident
  • Neglect

Circle D Transmission will not pay for any fluids replaced in the event of a rebuild kit failure.

Under no circumstances shall there be any labor warranty or other warranty coverage on Circle D Transmission Kits beyond the replacement of individual rebuild kit components. We will not provide you with any cash refund except as may be required by law. Consequential and incidental damages are not recoverable under this warranty and are expressly excluded.

There is no warranty on broken parts such as, but not limited to, twisted splines, broken shafts, or broken planetaries.

Warranty issues will be considered on an individual basis.