• High line pressure
  • Harsh shifts
  • Low cooler flow
  • Loss of lube oil
  • Overheated transmission & converter


Wear of the OE pressure regulator shuttle valve sleeve due to continuous movement of the shuttle valve prevents proper line pressure control.


Install the drop-in Sonnax shuttle valve assembly with upgraded materials and increased critical valve-to-sleeve sealing engagement to restore hydraulic integrity and prevent future wear.

8L45, 8L90

Shuttle Valve Kit
Part No. 154740-09K

You need this if... View Instructions Find a Distributor

Vehicles with a GM 8L45 or 8L90 transmission may exhibit high line pressure that results in harsh shifts, loss of cooler and lube flow and overheating of the transmission and converter. These problems may be caused by continuous oscillation of the shuttle valve within the shuttle sleeve, creating excessive wear and a path for balance line pressure at the pressure regulator valve to exhaust. This prevents proper positioning of the pressure regulator valve and can keep it in the higher pressure position. When in this position, bypass of excess pressure is not allowed and converter/lube/cooler feed pressure is greatly reduced.

Sonnax drop-in shuttle valve kit 154740-09K has upgraded materials and minimal clearances to prevent wear and restore proper hydraulic control. The length of the critical shuttle valve diameter has also been lengthened to provide better sealing and durability of the assembly.

  • Shuttle sleeve is manufactured from highly wear-resistant billet aluminum to prevent wear
  • Hardcoat anodized aluminum valve combats premature wear
  • Critical valve spool made 30% longer than OE for added sealing and durability
  • Drop-in Zip Valve™ parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • Valve
  • Sleeve

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 8L45, 8L90 Valve Body Layout

GM 8L45, 8L90 Valve Body Layout
  • 8L45, 8L90 Shuttle Valve Kit 154740-09K
  • 8L45, 8L90 Shuttle Valve Kit 154740-09K

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.

8L45, 8L90 Shuttle Valve Kit Vacuum Test Locations