Sonnax 37947-03K Boost Valve Kit Increased Ratio for Ford 4R44E 4R55E 5R44E 5R55E

The Sonnax 37947-03K is an increased ratio boost valve kit designed to resolve common transmission issues in Ford 4R44E, 4R55E, 5R44E, and 5R55E automatic transmissions. This kit features increased ratios for slightly higher line pressures compared to the OE specification, making it ideal for improving shift quality and hydraulic performance.

Common Problems This Kit Solves:

• Soft shifts and delayed reverse engagement
• Poor modulator control and low line pressure in reverse
• Worn boost valves allowing reverse and/or TV pressure to cross leak or exhaust

Key Features:

• Sleeves manufactured from highly wear-resistant aluminum alloy
• Hardcoat anodized aluminum valve combats premature wear
• Tight tolerances restore the hydraulic integrity of the assembly
• Drop-in Zip Valve™ parts install quickly and easily
• Improves engagement related to loss of boost oil and increased line rise in forward and reverse

This kit may be used to replace either the 3-circuit or 2-circuit OE sleeve designs, making it a versatile solution for transmission rebuilders. For applications requiring stock line pressure levels, Sonnax also offers the OE ratio kit 37947-01K.