Overview
The ZF 4616.120.404 PRESSURE REGULATOR is a precision-engineered hydraulic control component specifically designed for the WG 65 Series transmission family. This OEM genuine part modulates hydraulic pressure within the valve body assembly, ensuring consistent clutch pack engagement and smooth gear shifts under varying load conditions. The SKU 4616.120.404 directly interfaces with the main control bore, where it receives pilot pressure signals and adjusts output flow to maintain optimal line pressure. It is mounted internally within the 4616101066 TRANSMISSION HOUSING, which provides the structural foundation for the entire hydraulic circuit. Without this regulator, the transmission cannot maintain the precise pressure thresholds required for torque converter lockup or shift timing.
Symptoms of Failure
- Erratic shift timing and gear slipping under load: A worn 4616.120.404 often causes delayed or harsh upshifts, particularly when climbing grades or carrying heavy payloads. Operators may notice the transmission hunting between gears without a steady pressure signal.
- Oil leaks around the valve body area: Degraded internal seals on the pressure regulator allow ATF to bypass, leading to visible drips from the transmission pan or bell housing. This is frequently misdiagnosed as a main seal failure.
- Torque converter shudder at low RPM: Inconsistent regulation of lockup clutch pressure produces a vibration or shudder during light throttle acceleration, especially between 30-45 mph. This symptom often worsens as transmission fluid temperature rises.
- High or low line pressure readings: Diagnostic scans may reveal pressure deviations exceeding 15 PSI from factory specifications, triggering fault codes for pressure control solenoid circuits.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4616.120.404 |
| OEM Reference | ZF 4616.120.404 |
| Material | Hardened steel spool with aluminum alloy body |
| Weight | 0.42 kg (0.93 lbs) |
| Overall Length | 85 mm |
| Spool Diameter | 18 mm |
| Operating Pressure Range | 4–22 bar (58–319 PSI) |
| Seal Type | PTFE energized lip seal |
Compatibility
This pressure regulator is engineered for the ZF WG 65 Series, which includes the WG65, WG80, WG100, WG120, WG150, WG180, and WG200 transmission models. These units are commonly found in medium-duty trucks, municipal vehicles, and off-highway equipment. The 4616.120.404 is also cross-compatible with certain early WG250 variants that share the same valve body architecture. Always verify the transmission serial number against ZF technical bulletins before installation. The regulator works in conjunction with the 0636011118 HEXAGON SCREW for secure mounting, and interfaces with the 4616301307 HOUSING or 4616301309 HOUSING depending on the specific valve body revision.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4616101066 | TRANSMISSION HOUSING | Main structural casing for gear train and valve body |
| 0636011118 | HEXAGON SCREW | Fastener for pressure regulator mounting bracket |
| 4616301307 | HOUSING | Valve body cover for WG65 series |
| 4616301309 | HOUSING | Alternate valve body cover for later production runs |
| 0636011038 | HEXAGON SCREW | Bolt for housing-to-case attachment |
| 0636016015 | HEXAGON SCREW | High-tensile fastener for valve body retention |
| 0631306085 | CYLINDRICAL PIN | Alignment dowel for precision housing positioning |
| 0634313118 | O-RING | Hydraulic seal for pressure regulator bore |
| 0636304019 | SCREW PLUG | Port closure for test points and drain passages |
| 0634801152 | SEALING RING | Copper crush washer for high-pressure fittings |
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