Vehicles with a GM 8L45 or 8L90 transmission may exhibit high or low line pressure that results in harsh shifts, burnt clutches, loss of cooler and lube flow and overheating of the transmission and converter. These problems may be caused by wear of the pressure regulator bore casting at the VFS signal port area and/or at the shuttle valve sleeve. Wear at the inboard port of the pressure regulator bore allows VFS (throttle) signal pressure to leak, preventing proper action of the pressure regulator valve and potentially allowing it to remain in the low line pressure position. Wear of the shuttle sleeve due to continuous oscillation of the shuttle valve creates a path for balance line pressure at the pressure regulator valve to exhaust, resulting in excessive low line pressure.

Sonnax pressure regulator and O-ringed shuttle valve kit 154740-29K restores hydraulic integrity to the lineup by addressing wear that subjects the transmission to either excessive high or low line pressure with upgraded materials, O-ringed sleeve, and unique designs. The pressure regulator valve has been designed with a lengthened spring pocket spool at the VFS signal port area, which provides over double the sealing capability to this critical end of the valve and allows it to operate in unworn portions of the bore. The length of the critical shuttle valve diameter has been significantly lengthened to provide better sealing and durability of the assembly.

• Hardcoat anodized aluminum valves and highly wear-resistant billet aluminum sleeve combat premature wear
• O-Ringed sleeve provides positive seal against worn castings
• Pressure regulator valve VFS signal spool 200% longer than OE and operates in unworn area of the bore
• Critical shuttle valve spool made 30% longer than OE for added sealing and durability
• Drop-in Zip Valve™ parts install quickly and easily