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  • Low clutch oil pressure
  • No 4th
  • No 5th
  • No 6th
  • Harsh shifts
  • Flare shifts


Excess actuator feed limit (AFL) bore wear allows pressure loss that leads to driveability concerns.


Recover hydraulic control and renew shift performance by reconditioning the bore and installing Sonnax oversized AFL valve.

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

Oversized Actuator Feed Limit Valve
Part No. 144740-01

You need this if... View Instructions

The function of the actuator feed limit (AFL) valve is to provide regulated pressure to shift solenoids. Wear in the AFL bore causes low clutch pressure and results in transmission slips/harsh shifts. This eventually leads to a loss of 4th through 6th gears, and finally the loss of transmission function. Reconditioning the bore and installing Sonnax oversized AFL valve 144740-01 restores hydraulic control for revived shift operation in all ranges for GM Gen. 1 6T40, 6T45, 6T50 and GM Gen. 2 6T40, 6T45, 6T50 units.

  • Hardcoat anodized aluminum valve combats premature wear
  • Annular grooves help center valve in bore to reduce future side-load wear

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

September 18, 2014

GM 6T40, 6T45, 6T50 Series Identification Guide

Topics: Identification Guides Transmission GM 6T40 (Gen. 2) Transmission 6T45 (Gen. 2) Transmission 6T50 (Gen. 2) Transmission 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 01 in combogen1
  • 144740 01 in combogen2
  • 144740 01

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 01 in gen1test
  • 144740 01 in gen1test