SunCoast 6L80E Category 1 Transmission 

Pricing: $4,695.00

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Refundable Core Charge: $2,000.00


6L80E/6L90E Transmission includes the following

  • New Selective Pump Thrust Washer
  • New Filter Assembly
  • Torrington Thrust Bearing Kit
  • New Bushing Kit
  • New Molded Piston Kit
  • All New Steel Module
  • Raybestos GPZ Friction Module
  • Raybestos 3-5-R Z Pak
  • Raybestos 4-5-6 Z Pak
  • SunCoast Overhaul Kit
  • New Pan Gasket
  • Sonnax Zip Kit
  • Heavy Duty 4-5-6 Backing Plate Setup

The 6L Platform

The 6L80 transmission was manufactured in Ypsilanti, Michigan, at the Willow Run Transmission facility. The 6L80 was a much different transmission than its predecessor and was intended to be replaced in 2006 when it was initially released. This new unit came with a new 32-bit controller integrated into the valve body that stayed in constant communication with the ECM via GM's new high-speed can bus network.

This new design approach in the 6L80 utilizes three-way, variable-bleed solenoids to improve shift quality and consistency which are constantly monitored and corrected by utilizing GM's new adaptive shift strategies. The deep first and second gear ratios of 4.02 and 2.36 offer ample torque multiplication with a nice, tight shift recovery. The 6L80 transmission comes with a factory rating of 440 ft. lbs of torque.

The Cat 1 6L80 Transmission

The Category 1 Suncoast 6L80 Transmission has everything that our Category 0 Transmission has with the addition of the Sonnax Zip Kit and the upgraded 4-5-6 piston and backing plate assembly.

The Frictions Kit

Raybestos® Powertrain GM 6L80 GPZ Clutch Pack® contains upgraded friction components manufactured with the unique blend of GPZ high energy fibers for ultimate stress and high-temperature durability. This kit also includes the 3-5 Reverse Z Pak® and 4-5-6 Z Pak® to provide solutions to common 6L80 transmission failure points. Z Paks are completely redesigned, single-sided clutch systems that outperform OE in torque and heat capacity, without coning.

Friction Material Composition

Raybestos Powertrain GPZ friction plates greatly increase transmission performance and durability. This state-of-the-art friction material far exceeds OE material to withstand high stress, high temperatures, and repeated cycling. GPZ's outstanding performance benefits are perfect for heavy-duty vehicles and high-stress driving. Testing of GPZ revolutionary friction material shows that it outperforms OE materials by as much as 20%. Plus, its performance improves as the power increases.

Recommended Use

High-stress, driving-enhanced performance applications, heavy-duty vehicles, commercial vehicles, daily-driven vehicles and as a problem solution for 3-5 Reverse and 4-5-6 clutch failure.

The Zip Kit

Sonnax Zip Kit 6L45-6L90-ZIP targets the root cause of multiple complaints by sealing the critical circuit pressure losses in the GM 6L45, 6L50, 6L80, 6L90 valve body. The kit contains uniquely designed parts to prevent the loss of pressures within the main line, clutch apply control, solenoid feed and lockup control circuits. The kit also seals multiple circuits known to suffer from end plug leakage or poor checkball sealing. No special tools are required for installing these parts.

The Zip Kit quick guide provides clear and easy instructions on one sheet to get the unit sealed up and back on the road fast. In addition to general rebuilding tips and technical information, the technical booklet included in this kit contains vacuum testing information and locations at other key areas of the valve body.

  • No reaming required
  • Installs quickly with no special tools required
  • Uniquely designed parts address root causes of valve body complaints by sealing critical pressure circuits
  • Detailed technical booklet included with in-depth rebuild and inspection tips for comprehensive valve body repair


  • Pressure Regulator Valve Kit
  • Boost Valve Kit
  • Clutch Select Valve Spring Kit
  • Compensater Feed Regulator Valve Kit
  • TCC Regulator Valve, Spring, Shuttle Valve and End Plug
  • O-Ringed End Plug Kit
  • Actuator Feed Limit Valve, Sleeve and Spring
  • Center Support Seal Kit
  • Vacuum Test Nut
  • Checkballs (8) .250" dia.

The Backbone of the 4-5-6 Clutch

GM 6L80 and 6L90 transmissions often suffer failure of the 4-5-6 clutch assembly due to OE design shortcomings. Insufficient clutch piston-to-plate apply surface area causes clutch plate failure, especially when apply pressures exceed OE specifications. The other problem is flexing and bowing of the backing plate (coning), which is a primary source of clutch failure.

The heavy duty Sonnax 4-5-6 clutch apply piston kit 104960-01K addresses these weak areas in two ways:

  1. A modified OE clutch apply piston and piston dam are used in conjunction with a specially-designed Sonnax piston apply ring.
  2. A more rigid backing plate

The Sonnax apply ring increases surface area between the apply piston and OE waved clutch plate, resulting in more even distribution of apply force to clutch plates. The Sonnax backing plate minimizes the flexing/bowing when clutch is applied, drastically reducing the likelihood of clutch plate distortion.

  • Use with stock clutches and OE waved plate
  • Solid backing plate design outperforms OE and aftermarket plates
  • Increased apply ring surface area improves clutch apply
  • Reduces heat buildup


  • Apply Piston
  • Apply Ring
  • Piston Dam
  • Backing Plate



Shipping Information

  • Item Requires Shipping
  • 350.0 lbs.
  • W48.0000” x H48.0000” x L32.0000”
  • This item will require a special quote for shipping charges.

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