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
| EPC PSI | 37947-01K (OE Ratio) |
37947-03K (Increased Ratio) |
||
|---|---|---|---|---|
| Line | Reverse | Line | Reverse | |
| 30 | 107 | 135 | 114 | 143 |
| 75 | 178 | 224 | 194 | 243 |
| 120 | 250 | 313 | 275 | 343 |
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
Symptoms:
- Delayed Reverse
- Soft shifts
- Low line pressure
- Poor modulator control
