Servo apply oil is fed through the center of the case bridge and into the servo pin, reacting on the cover side of the piston. As the case pin bore wears, this apply oil will leak into the barrel area of the case. This negatively affects shift timing and servo/band apply pressure. Servo release pressure is fed through the case and into the spring side of the piston. As pin bore wear increases, release oil will cross leak into the apply circuits, exhausting at the shift valves. In reverse, both servos are charged from the release side, so pin bore wear results in delayed reverse. The 5R55N, 5R55W and 5R55S are prone to foaming the fluid in the sump from excess exhaust and valve body wear. This results in fluid out the vent and improper fill indications.
Contact a Sonnax Parts Distributor.