Line modulator bore wear in Ford CD4E and Mazda LA4A-EL units reduces TV oil pressure working on the main regulator valve to boost line pressure. This can be discovered during vehicle pressure testing as lower maximum line in Reverse and Drive. Lower line will result in longer soft shifts under heavier throttle or flare on 1-2 shift. The worn bore also reduces oil pressure supplied to the 2-4 accumulator and servo apply. Harsh shifts and — in some instances — high line pressure can result if the valve will not stroke open to control/reduce 2-4 pressure.
Sonnax oversized line modulator valve kit 73840-27K allows the bore to be refurbished and hydralic integrity restored for proper line and TV/EPC pressure control.