• High EPC pressure
  • Low EPC pressure
  • High line pressure
  • Low line pressure
  • Erratic shifts


The constant oscillation of the steel pressure modifier valve wears the bore, resulting in loss of valuable EPC oil.


Seal oil at the balance end of the pressure modifier valve to correct line pressure. Seal line pressure oil at the middle spools to prevent low line pressure.


Required tool kit 74846-TL4 is no longer in production. Contact your distributor to see if they still have this product available.


Oversized Pressure Modifier Valve
Part No. 74846-04

You need this if... View Instructions Find a Distributor

When the balance spool bore in Mazda G4FA-EL units wears, the valve won't stroke to regulate EPC pressure. If the middle spool bore wears, line pressure will be allowed to exhaust. Sonnax oversized pressure modifier valve 74846-04 restores hydraulic integrity to the circuit by sealing these locations in the bore.

It is highly recommended that the pressure regulator bore also be checked for wear. A worn pressure regulator bore can result in low/high line pressure, harsh shifts, lack of cooler flow, and/or blued converters.

  • Hardcoat anodized aluminum valve combats premature wear
  • OE spring can be reused thanks to shortened spring seat depth that compensates for the oversized valve
  • GF4A-EL Oversized Pressure Modifier Valve 74846-04
  • GF4A-EL Oversized Pressure Modifier Valve 74846-04

You need this if...

To wet air test the bore for leakage, place a small amount of oil in the balance EPC circuit. While holding the valve in the unstroked position, follow with low air pressure (Figure 1). There should be minimal or no leakage through the neighboring line port. If excessive leakage occurs, the bore should be reamed and the OE valve replaced.

GF4A-EL Oversized Pressure Modifier Valve Vacuum Test Locations