Overview
The ZF 4644.305.028 SPRING HOLDER RING is a critical retention component engineered specifically for the WG200 series transmission. This OEM genuine part secures the spring assembly within the clutch pack, ensuring consistent pressure application during gear shifts. Positioned inside the drum housing, the ring prevents axial displacement of the spring mechanism under high-torque loads. The SKU 4644.305.028 is precision-machined to ZF’s exacting tolerances, making it indispensable for maintaining hydraulic circuit integrity in heavy-duty applications.
Symptoms of Failure
- Erratic gear engagement or delayed shifting: When the spring holder ring fatigues, the spring pack loses preload, causing hesitation between gear changes—a common issue in WG200 units.
- Transmission oil seepage near the drum housing: A deformed or cracked ring compromises the seal interface, leading to gradual fluid loss around the TRANSMISSION HOUSING.
- Audible rattling or metallic noise during deceleration: Worn rings allow spring oscillation, producing distinct clattering sounds that worsen under load.
- Intermittent clutch slip under heavy load: Insufficient spring retention reduces clutch pack clamping force, causing power loss during uphill or loaded operation.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.305.028 |
| Material | Spring steel (DIN 17222) |
| Outer Diameter | 148 mm |
| Inner Diameter | 132 mm |
| Thickness | 4.2 mm |
| Weight | 0.18 kg |
| OEM Reference | ZF 4644.305.028 |
| Surface Treatment | Phosphate coated |
Compatibility
This spring holder ring is designed for ZF WG180, WG200, and WG210 series transmissions used in municipal trucks, fire apparatus, and construction vehicles. It directly interfaces with the DISCONNECTION assembly and the OUTPUT FLANGE unit. For secure mounting, pair it with the HEXAGON SCREW (M8x20 grade 10.9). Always verify your transmission’s serial number before ordering, as WG200 variants may use different spring configurations.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644105424 | DISCONNECTION | Clutch disengagement mechanism |
| 4644303538 | OUTPUT FLANGE | Driveshaft connection interface |
| 0636021036 | HEXAGON SCREW | Fastener for housing assembly |
| 4644101224 | TRANSMISSION HOUSING | Main structural casing |
| 4644301346 | TRANSMISSION HOUSING | Alternate housing variant |
| 0730365067 | TYPE PLATE | Identification label |
| 4644106300 | SHIFT SYSTEM | Gear selection actuator |
| 4644306500 | COVER PLATE | Access panel for valve body |
| 4644159311 | SHIFT SYSTEM | Secondary shift mechanism |
| 4644306563 | VALVE BLOCK | Hydraulic control manifold |

