Ford 4R70W 4R75W Transmission Overdrive Servo Regulator Common problems with a 4R70W are a burned overdrive band, loss of 4th gear, and/or a 4-3-neutral shift pattern. These problems can be caused by wear at the inside diameter of the overdrive servo regulator boost valve sleeve, due to constant oscillation. Excessive wear allows valuable overdrive oil to leak, preventing the proper regulation of the overdrive servo. The Sonnax replacement assembly maintains critical tolerances that re-establish the hydraulic integrity of the circuit. Hard-coat anodized valve and high-grade aluminum sleeve resist wear. Closely toleranced sleeve improves sealing.