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. Note 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. Contents Pressure Regulator Valve Matching Outer Spring Boost Valve Boost Sleeve Drill Bit Checkballs (2) 1 Extra