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  • Code P0741, P0742
  • Failsafe mode
  • Harsh shifts
  • Harsh TCC apply
  • High TCC slip RPM
  • Loss of fuel economy
  • Overheated fluid


Bore wear at the TCC regulator valve reduces TCC apply and converter charge pressure. A stuck TCC regulator valve causes either TCC slip or harsh apply.


Ream to restore the bore and install Sonnax oversized valve kit to restore proper valve function.

6L45, 6L50, 6L80, 6L90

Oversized TCC Regulator Valve Kit
Part No. 104740-07K

You need this if... View Instructions

Vehicles with GM 6L45, 6L50, 6L80, 6L90 series transmissions may have a number of TCC apply problems. Bore wear at the TCC regulator valve can cause no TCC apply or slipping on engagement, harsh shifts, loss of performance and fuel economy, and fluid overheat. If the valve is stuck in the apply position, the result is harsh TCC apply. If the valve is stuck in the release position, no TCC apply or TCC slip will result. Installing Sonnax oversized TCC regulator valve kit 104740-07K will restore proper valve function, resulting in proper TCC apply.

  • Valve is hardcoat anodized to reduce wear
  • Restores proper valve function and TCC apply
  • TCC Regulator Valve
  • Shuttle Valve
  • End Plug

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 6L45, 6L50, 6L80, 6L90 Valve Body Layout

Gm 6l45 vbl thumb

August 21, 2013

GM 6L45-6L90 Vacuum Test Guide

Topics: Vacuum Testing Vacuum Test Guides Transmission GM 6L90 Transmission 6L80 Transmission 6L50 Transmission 6L45 Transmission

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September 30, 2005

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

Gregg Nader

Topics: Diagnostics And Theory Transmission

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  • 104740 07k combo
  • 104740 07k

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

  • 104740 07k test