Overview
The ZF 4644.108.031 COUNTERSHAFT is a critical internal component designed specifically for the WG 180 series heavy-duty transmission. This genuine OEM part serves as the primary torque-transfer spindle, meshing directly with multiple gear sets to facilitate smooth ratio changes under high load conditions. Positioned within the lower gear train assembly, the countershaft (SKU: 4644.108.031) supports the idler gears and distributes rotational force from the input shaft to the output shaft. Its precision-ground splines and hardened bearing journals ensure minimal backlash and long-term durability in demanding industrial applications such as construction, mining, and municipal vehicles.
Symptoms of Failure
- Gear grinding or hard shifting: When the countershaft bearing surfaces wear, gear engagement becomes noisy and difficult, often accompanied by a distinct metallic chatter during acceleration.
- Vibration under load: A worn 4644.108.031 can cause noticeable driveline shudder, particularly in lower gears, as the shaft loses concentricity and induces imbalance.
- Oil contamination with metallic debris: Flaking or spalling on the countershaft journals will shed fine steel particles into the transmission fluid, visible during drain intervals.
- Intermittent power loss: If the countershaft splines strip or crack, torque delivery becomes erratic, leading to sudden slippage or complete loss of drive in specific gear ranges.
Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number | 4644.108.031 |
| Material | Case-hardened alloy steel (20MnCr5 equivalent) |
| Overall Length | ~485 mm |
| Bearing Journal Diameter | 55 mm (input side) / 50 mm (output side) |
| Weight | ~8.7 kg |
| OEM Reference | ZF 4644.108.031 (Genuine) |
| Surface Treatment | Black oxide / phosphate coating |
Compatibility
This genuine ZF countershaft is engineered primarily for the WG 180 series transmissions. Based on its spline count and bearing geometry, it is also compatible with the WG 200 and select WG 160 variants that share the same internal architecture. Always verify the serial number of your transmission housing before installation. The countershaft works in concert with the 4644101080: TRANSMISSION HOUSING and the 4644301333: HOUSING to maintain proper alignment. For identification, the 0730365125: TYPE PLATE should be cross-referenced, and the assembly is secured using the 0631311009: GROOVED STUD.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101080 | TRANSMISSION HOUSING | Main structural casing for gear train |
| 4644301333 | HOUSING | Intermediate support housing for shafts |
| 0730365125 | TYPE PLATE | Identification tag for transmission model |
| 0631311009 | GROOVED STUD | Fastener for housing alignment |
| 0636305019 | SCREW PLUG | Seals oil passages in the housing |
| 4644301247 | THREADED BUSH | Wear insert for shift rail bore |
| 0634303485 | O-RING | Seals housing joints against leaks |
| 4644106055 | SHIFT SYSTEM | Controls gear engagement via fork |
| 4642306050 | COVER PLATE | Encloses the shift mechanism |
| 4644306464 | GASKET | Prevents fluid seepage between covers |
