• Code 28, 1744, 1740
  • High line pressure
  • Cracked drum
  • Planetary failure
  • Bushing failure
  • Loss of lube oil
  • No cooler flow during failsafe


Worn casting bores at the pressure regulator and converter regulator valves, and insufficient cooler and converter flow.


Sonnax oversized PR valve restores the balance circuit to correct high line pressure and guards against excess EPC/TV pressure. Sonnax PR valve and converter regulator valve have modifications to properly regulate converter and cooler flow.


Oversized Pressure Regulator & Converter Regulator Valve Kit
Part No. 73840-RK

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Ford CD4E and Mazda LA4A-EL transmissions frequently exhibit symptoms of lube failure, harsh shifts and line pressure instability. Wear of the pressure regulator balance circuit (opposite end from spring) creates high line pressure. High line pressure is known to break up parts, but also positions the valve to reduce the flow into converter/cooler circuits. If the vehicle goes into failsafe (no EPC control) the lube circuit can be shut off completely on the OE valve. The OE converter regulator valve shuts off cooler/converter flow at 90-100 psi.

Sonnax oversized pressure regulator and converter regulator valve kit 73840-RK featires a converter regulator valve and PR valve which work together to limit converter pressure, yet ensure flow continues during a failsafe condition.

  • Updated valves flow a safe regulated pressure into both the line and converter circuit, yet maintain control under low pump volume and high line conditions
  • Improved line-to-lube circuit allows full-time cooler flow
  • Includes an EPC pressure limit relief valve
  • Redesigned converter regulator valve has a lengthened spool to eliminate cooler pressure loss
  • Tapered spool design of the converter regulator valve ensures flow at extreme pressure
  • Hardcoat anodized aluminum valves combat premature wear and feature annular grooves to prevent side loading

This kit cannot address the loss of valve control at the converter bypass circuit. Wear at the bypass valve contributes to codes 628, 1740 and related converter slip codes. For information on that repair, see part number 73840-BK.

Reamer kit 73840-RTL is no longer in production but may be available from distributor inventory. F-73840-TL is available for use prior to installing 73840-RK.

  • Converter Regulator Valve
  • Converter Regulator Spring
  • Oversized Pressure Regulator Valve
  • Lubrication Plugs (4) 1 Extra
  • Rivets (3)

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

Ford CD4E Valve Body Layout

Ford CD4E Valve Body Layout

  • CD4E, LA4A-EL Oversized Pressure Regulator &  Converter Regulator Valve Kit 73840-RK
  • CD4E, LA4A-EL Oversized Pressure Regulator &  Converter Regulator Valve Kit 73840-RK