Overview
The ZF 4644.306.607 PISTON is a critical hydraulic actuation component engineered for the WG 150, WG 180, and WG 200 series powershift transmissions. This OEM genuine part functions as a pressure-responsive plunger within the valve body or clutch pack assembly, converting hydraulic fluid force into precise mechanical motion to engage or disengage specific gear sets. The SKU 4644.306.607 ensures exact dimensional tolerances and material hardness required for consistent shift quality under heavy-duty industrial loads. When paired with a robust TRANSMISSION HOUSING (4642101109) or a TRANSMISSION HOUSING (4642301205), this piston maintains the sealed integrity of the hydraulic circuit, preventing cross-contamination between lubrication and actuation channels.
Symptoms of Failure
- Erratic gear engagement or delayed shifting: A worn 4644.306.607 piston allows internal leakage, causing sluggish clutch application and hesitation when moving from neutral to drive or between forward ranges.
- Intermittent loss of hydraulic pressure: Cracks or scoring on the piston surface lead to pressure drops, often accompanied by whining noises from the pump as it compensates for the leak.
- Transmission overheating under light load: Failed pistons create constant slippage in the clutch packs, generating excessive heat that can warp nearby components like the GROOVED STUD (0631311009).
- Visible oil seepage from breather vents: When the piston seal degrades, pressurized fluid escapes past the bore, pooling around the bell housing or dripping from the TYPE PLATE (0730365125) area.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4644.306.607 |
| Material | Hardened alloy steel with phosphate coating |
| Outer Diameter | 48.5 mm ± 0.05 mm |
| Overall Length | 72.0 mm |
| Weight | 0.34 kg (0.75 lbs) |
| OEM Reference | ZF 4644.306.607 (Genuine) |
| Surface Finish | Ra 0.4 µm (ground) |
Compatibility
This piston is specifically designed for ZF WG series powershift transmissions, with primary application in the WG 150, WG 180, and WG 200 models. It is also compatible with select variants of the WG 160 series where the valve body uses the same 48.5 mm bore diameter. The 4644.306.607 piston interfaces directly with the shift system assembly; for complete hydraulic restoration, consider replacing the SHIFT SYSTEM (4644106324) and the PLATE (4644306598) simultaneously to ensure matched wear patterns.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4642101109 | TRANSMISSION HOUSING | Encloses gear train and supports bearing bores |
| 4642301205 | TRANSMISSION HOUSING | Alternate housing variant for WG 200 series |
| 0730365125 | TYPE PLATE | Identification tag with transmission serial number |
| 0631311009 | GROOVED STUD | Locating pin for clutch pack alignment |
| 4642301168 | SCREEN SHEET | Fine mesh filter for hydraulic oil return line |
| 4642301169 | SCREEN SHEET | Coarse mesh pre-filter for suction side |
| 0636100621 | HEXAGON SCREW | M8 bolt for securing valve body cover |
| 4642301186 | SCREEN SHEET | Secondary filter for clutch feed circuit |
| 4644106324 | SHIFT SYSTEM | Complete selector mechanism with detent springs |
| 4644306598 | PLATE | Thrust washer for planetary gear carrier |
