sonnax-black Facebook-color LinkedIn-color maillink printlink r_and_r_only SERVOFIX-logo-web Twitter-color VBFIX-logo-web video-logo-web warranty_only Youtube-color


  • Erratic TCC apply
  • Failsafe mode
  • Harsh shifts
  • Pressure control out-of-range codes
  • Shift codes
  • Slips, flares & bind-ups
  • Pressure switch codes


OE pressure switch laminate disc breached, preventing proper switch operation.


Salvage the transmission control unit and restore normal shift operation by installing a set of four seals and laminate discs from the Sonnax pressure switch rebuild master pack.

6L45, 6L50, 6L80, 6L90, 6T70 (Gen. 1), 6T75 (Gen. 1)

Pressure Switch Rebuild Master Pack
Part No. 124740-28K

View Instructions

Listed GM 6-speed transmissions often set various trouble codes related to failures of fluid pressure switches that are internal to the transmission electro-hydraulic control module (TEHCM). These codes may be accompanied by TCC apply problems or shift irregularities such as slipping, flares, harsh application, and bind-ups. As time goes by, the laminated portions of the pressure switches can breach, preventing normal switch operation. If more than one switch breaks down, failsafe mode can be triggered. Since switches cannot be obtained through OE channels, replacement of the TEHCM was the only previous remedy available.

It is no longer necessary to replace the expensive TEHCM assembly to rectify this concern. Installing Sonnax pressure switch rebuild master pack 124740-28K restores normal switch operation, eliminating codes and providing renewed shift performance in all ranges.

  • Allows salvage of expensive TEHCM
  • Installation tools included in kit

All I need to say is WOW! Since getting the new tools and kit, I have done 4 transmissions and all went great. I want to say thank you to Sonnax for creating a kit that makes working on these transmissions a little easier.

Continental Transmission
Bridgeview, IL

Before installing kit, test switches to verify proper electrical operation. Kit repairs laminate disc and seal failures only; it will not rectify electrical breakdown. See instructions for details.

  • Laminate Discs (40)
  • Seals (40)
  • Seal Installer
  • Piston
  • Seal Plunger
  • Laminate Installation Tool

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 6T70 (Gen. 1), 6T75 (Gen. 1) Valve Body Layout

Gm 6t70 6t75 vbl

October 27, 2014

Under Pressure: Shift Quality & Pressure Switches in TEHCM Applications

Topics: Transmission GM 6T45 (Gen.1) Transmission 6L90 Transmission 6L80 Transmission 6L50 Transmission 6L45 Transmission 6T50 (Gen. 1) Transmission 6T70 (Gen. 1) Transmission 6T75 (Gen. 1) Transmission 6T40 (Gen. 1) Transmission

Read Now

February 19, 2015

Transmission Report: Sometimes the Best Tools are FREE!

Topics: Vacuum Testing Transmission Report Newsletters Diagnostics And Theory Transmission

Read Now

October 28, 2014

Easy Pressure Switch Rebuilds for 6L- & Gen. 1 6T-Series Units

Topics: Rebuilding Tips Transmission GM 6L90 Transmission 6L80 Transmission 6L50 Transmission 6L45 Transmission 6T70 (Gen. 1) Transmission 6T75 (Gen. 1) Transmission

Watch Now

September 30, 2005

Anatomy of a Transmission: Oil Flow in the Pump-PR-Converter-Cooler Lube Circuits

Gregg Nader

Topics: Diagnostics And Theory Transmission

Read Now

  • 124740 28k