• Burnt clutches
  • Line pressure instability
  • Loss of fuel economy
  • No line rise
  • Pressure loss
  • Pressure switch codes
  • Shift concerns
  • TCC apply & release concerns
  • TCC codes


Loss of oil pressure due to worn components in critical circuits and/or pressure switch failure.


Recover hydraulic control, restore normal shift operation and save the transmission control unit by installing Sonnax Zip Kit. Drop-in parts install quickly and easily.

6T30 (Gen. 1), 6T40 (Gen. 1), 6T45 (Gen. 1), 6T50 (Gen. 1)

Zip Kit®
Part No. 6T40-ZIP

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Sonnax Zip Kit 6T40-ZIP targets the root cause of multiple concerns by sealing critical circuit pressure losses in GM Gen. 1 6T30/40/45/50 valve bodies. The kit contains uniquely-designed parts to prevent the loss of pressures within the main line, clutch apply control, actuator feed, compensator feed and lockup control circuits. The kit also seals multiple circuits known to suffer from end plug leakage or poor checkball sealing. No separate special tools are required for installing these parts.

Replacement pressure switch seals and laminate discs in this Zip Kit address various trouble codes related to failures of fluid pressure switches which are internal to the transmission electro-hydraulic control module (TEHCM).

The Zip Kit quick guide provides clear and easy instructions on one sheet to get the unit sealed up and back on the road quickly. 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.

  • Drop-in Zip Valve parts install quickly and easily, no reaming or special tools required
  • Uniquely designed parts address root causes of valve body concerns by sealing critical pressure circuits
  • Detailed technical booklet included with in-depth rebuild and inspection tips for comprehensive valve body repair
  • Allows salvage of expensive TEHCM
Learn More About Zip Valve™ Drop-In Repairs
  • Pressure Switch Rebuild Kit
  • Rivets (2) 1 Extra (Not Shown)
  • Compensator Feed Regulator Valve Kit
  • TCC Regulator Apply Valve, Shuttle Valve, End Plug, Spring & O-rings 2 O-Rings, 1 Extra
  • AFL Valve, Sleeve, Spring & Retainer
  • End Plugs (5)
  • O-Rings (7) 2 Extra
  • Checkballs (6) .250" Dia.
  • Drill Bit .062" Dia. (Not Shown)
  • Aluminum Plugs (2) .062" Dia., 1 Extra (Not Shown)

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM 6T30/40/45/50 (Gen. 1) Valve Body Layout

GM 6T30/40/45/50 (Gen. 1) Valve Body Layout

  • 6T30 (Gen. 1), 6T40 (Gen. 1), 6T45 (Gen. 1), 6T50 (Gen. 1) Zip Kit® 6T40-ZIP


Zip Kit® Video - The First Step in Correcting Common Shift Problems
Sonnax Zip Kit

The Sonnax ZIP KIT®

The First Step in Correcting Common Shift Problems

It's easy to restore and extend vehicle shift quality with Zip Kits. Uniquely designed, drop-in Sonnax parts target the root cause of valve body complaints and stop critical circuit pressure losses in the most common problem areas of the transmission.

Learn More About Sonnax Zip Kits