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


Continuous oscillation of pressure regulator valve results in excess bore wear, causing erratic line pressure and/or restricting cooler/lube flow. Wear at the boost sleeve induces Reverse issues.


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

6L45, 6L50, 6L80, 6L90

Oversized Pressure Regulator & Boost Valve Kit
Part No. 104520-07K

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. Wear at boost sleeve leads to loss of correct Reverse pressure.

Reconditioning the bore and installing Sonnax oversized pressure regulator and boost valve kit 104520-07K re-establishes the hydraulic integrity of these circuits for proper line pressure control in all ranges.

  • Oversized pressure regulator valve and matched spring restore OE function
  • Annular grooves help center valves in bore to reduce future side-load wear
  • Hardcoat anodized aluminum valves combat premature wear.

Pump must be removed to install this kit. Use of the VB-06 is required with the VB-FIX reaming fixture for this installation unless the stator support shaft is removed from the pump body.

  • Pressure Regulator Valve
  • Matching Outer Spring
  • Boost Valve
  • Boost Sleeve
  • 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 07k combo
  • 104520 07k
  • 104520 07k 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 07k test