5R55N units commonly experience low line pressure and delayed engagements, typically resulting in pressure out-of-range codes, burnt forward clutches or intermediate bands. Bore wear at the VFS1 (PCA) and VFS2 (PCB) locations allows modulated line pressure to exhaust instead of feeding the overdrive, intermediate or low/reverse servos or the coast clutch, causing the complaints and damage. Install Sonnax PCA/PCB modulator valve kit 56947J-49K after refurbishing the bore to restore hydraulic control and optimum line pressure feed to affected circuits. Hard anodized material and annular grooves provide a long lasting repair that can beused in either location.
A vacuum at either port indicated fails, or if visual wear is detected at the inboard overlap valve bores.