8L45, M5N, M5T

Symptoms:

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

Cause:
Wear of the OE pressure regulator valve casting bore and shuttle valve sleeve due to continuous valve oscillation prevents proper line pressure control.

Correction:
Install the drop-in Sonnax pressure regulator and shuttle valve kit with upgraded materials and increased critical valve-to-bore sealing engagements to restore hydraulic integrity and prevent future wear.

Vehicles with a GM 8L45 or 8L90 transmission may exhibit high or low line pressure that results in harsh/soft 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 continous 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.

The Sonnax drop-in pressure regulator and shuttle valve kit restores hydraulic integrity to the lineup by addressing wear that subjects the transmission to either excessively high or low line pressure with upgraded materials 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
• 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

Contents:

• Pressure Regulator Valve
• Spring
• Shuttle Valve
• Shuttle Sleeve

SONNAX Installation Instructions