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  • Loss of fuel economy
  • Low TCC apply pressure
  • Overheated fluid & TCC lining
  • TCC slip
  • Code P0741
  • Code 742
  • No lockup
  • Harsh TCC apply


Bore wear at the TCC regulator valve reduces TCC apply and converter charge pressure. If valve sticks, TCC slip or harsh apply will result.


Recover hydraulic control and renew TCC performance by reconditioning the bore and installing Sonnax oversized TCC regulator valve kit.

6T30, 6T40 (Gen. 1), 6T40 (Gen. 2), 6T45 (Gen. 2), 6T45 (Gen.1), 6T50 (Gen. 1), 6T50 (Gen. 2)

Oversized TCC Regulator Valve Kit
Part No. 144740-16K

You need this if... View Instructions

Vehicles equipped with GM Gen. 1 and Gen. 2 6T40/45/50 transmissions can exhibit a number of TCC apply issues caused by bore wear at the TCC regulator valve. Slipping TCC, no TCC apply, fluid overheat and suffering fuel economy are common results of this wear. If the valve becomes stuck in the apply position, harsh TCC apply will be the consequence. If the valve is stuck in the release position, no TCC apply or TCC slip will occur. Installing Sonnax oversized TCC regulator valve kit 144740-16K re-establishes correct valve-to-bore clearances, restoring normal TCC operation.

  • Lengthened spools for additional bore contact and support
  • Hardcoat anodized aluminum valves combat premature wear
  • Annular grooves help center valves in bore to reduce future side-load wear
  • Shuttle Valve
  • End Plug
  • Spring
  • O-ring
  • Regulator Valve

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 6T40 (Gen. 1), 6T45 (Gen.1), 6T50 (Gen.1) Valve Body Layout

Gm 6t40 gen1 vbl thumb

GM 6T30 & 6T40, 6T45, 6T50 (Gen. 2) Valve Body Layout

6t40 gen2 vbl thumb

October 31, 2014

GM 1st Gen. 6T40, 6T45, 6T50 Vacuum Test Guide

Topics: Vacuum Test Guides Vacuum Testing Transmission GM 6T45 (Gen.1) Transmission 6T50 (Gen. 1) Transmission 6T40 (Gen. 1) 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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May 25, 2017

GM 6T30 & 6T40, 6T45, 6T50 (Gen. 2) Vacuum Test Guide

Topics: Vacuum Test Guides Transmission GM 6T40 (Gen. 2) Transmission 6T45 (Gen. 2) Transmission 6T50 (Gen. 2) Transmission 6T30 Transmission

Read Now
  • 144740 16k combo
  • 144740 16k

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.

  • 144740 16k vacuum