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


  • Burnt clutches
  • Clutch slippage
  • Harsh shifts
  • High line pressure
  • Low cooler flow
  • Low line pressure
  • No cooler flow
  • Overheated transmission
  • Soft shifts
  • Converter concerns


Continuous oscillation of pressure regulator valve results in excess bore wear, causing erratic line pressure and/or restricting cooler/lube flow.


Recover hydraulic control and renew line pressue performance by installing Sonnax pressure regulator valve kit.

6L45, 6L50, 6L80, 6L90

Pressure Regulator Valve Kit
Part No. 104520-03K

You need this if... View Instructions

GM 6L45, 6L50, 6L80 and 6L90 units may exhibit multiple line pressure and cooler/converter/lube flow problems due to excess wear in the pressure regulator bore. Deterioration at the balance spool end allows critical fluid loss, resulting in high line pressure, harsh shifts, and overheating due to reduced cooler/converter flow. Wear at the outboard spool robs converter feed pressure and lowers line pressure, resulting in soft shifts and burnt clutches. Installing Sonnax pressure regulator valve kit 104520-03K restores the hydraulic integrity of these circuits for proper line pressure control in all ranges.

  • Hardcoat anodized aluminum valve combats premature wear
  • Lengthened critical spools operate in non-worn portion of bore for added stability and wear prevention.
  • Annular grooves help center valve in bore to reduce future side-load wear
  • No reaming or special tools required

Pump must be removed to install kit.

  • Valve
  • Drill Bit
  • Checkballs (2) 1 Extra

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

Read 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
  • 104520 03k combo
  • 104520 03k valve
  • 104520 03k tools

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.

  • 104520 03k test