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Symptoms:

  • Low maximum line pressure
  • Low EPC pressure
  • Code P0741
  • TCC slip
  • Flare shifts

Cause:

The OE relief valve design and inconsistent casting pocket depth prevent proper cracking pressure at both the EPC and TCC relief valve locations.

Correction:

Replace the OE T-shaped relief valve and spring with the Sonnax checkball and spring kit to ensure proper and consistent seating and relief pressure.

4R44E, 4R55E, 5R44E, 5R55E

EPC & TCC Relief Valve Kit
Part No. 37947-40K


View Instructions

The OE relief valve design and inconsistent casting pocket depth prevent proper cracking pressure at both the EPC and TCC relief valve locations. The OE relief pressures have been tested at between 40-180 psi, while the optimal range should be around 115-120 psi. This inconsistent pressure range can result in high/low EPC and line pressure, shift complaints and various converter complaints. Sonnax has developed a replacement relief valve kit that can be used in either the EPC or TCC relief pocket locations. The kit contains a .250" diameter steel checkball, which provides more consistent sealing against the separator plate. A replacement relief spring is also included for accurate pressure control. A guide spring is also included to fit securely into the machined casting pocket, which ensures the relief spring stays properly centered, and that pressure exhausts sufficiently. Machining of the casting pocket is required (using a drill press or hand-held drill) to establish an accurate depth for pressure control.

  • Ensures accurate and consistent pressure relief at both the EPC and TCC circuits.
  • Relief Spring
  • Guide Spring
  • Checkball

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 4R/5R44E, 4R/5R55E Valve Body Layout

Ford 4r 5r44e thumb
  • 37947 40k combo
  • 37947 40k