4R44E 4R55E 5R44E 5R55E Transmission Boost Valve Kit Sonnax 37947-01K OE Ratio

Some typical problems in 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 kit 37949-03K. The 37947-01K has OE spool ratios, to return line rise to stock condition. The 37949-03K assembly has increased ratios for slightly higher line pressures.

• Sleeves are manufactured from highly wear-resistant aluminum alloy.
• Valves are made from hard-anodized aluminum for better wear resistance.
• 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