Worn casting bores at the pressure regulator and converter regulator valves, and insufficient cooler and converter flow.
The oversized PR valve restores the balance circuit to correct high line pressure and guards against excess EPC/TV pressure. The PR valve and converter regulator valve have modifications to properly regulate converter and cooler flow.
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.
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.
Contact a Sonnax Parts Distributor.