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Manufacturer Part Number: 37947-03K

Other Part Number: S56741FA

Brand: Sonnax

4R44E, 4R55E, 5R44E, 5R55E

Boost Valve Kit
Part No. 37947-03K

Increased Ratio

Some typical problems in Ford 4R44E, 4R55E, 5R44E and 5R55E units are soft shifts, delayed Reverse, poor modulator control and/or low line pressure in Reverse. A worn boost valve is often the cause, allowing Reverse and/or TV pressure to cross leak or exhaust. Sonnax offers two replacement boost valve kits for these units: the OE ratio kit 37947-01K and the increased ratio boost valve kit 37947-03K. The 37947-01K has OE spool ratios, to return line rise to stock condition. The 37947-03K assembly has increased ratios for slightly higher line pressures.
  • Sleeves are manufactured from highly wear-resistant aluminum alloy
  • Harcoat anodized aluminum valve combats premature wear
  • Tight tolerances restore the hydraulic integrity of the assembly
  • Kits improve engagement related to loss of boost oil and increased line rise in Forward and Reverse

Pressure Comparison Between OE and Increased Ratio Boost Valves

OE sleeves may come in either a 3- or 2-circuit design. Boost valve kits 37947-01K and 37947-03K may be used to replace either version.

  • Valve
  • Sleeve

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