Overview
The ZF 4646.108.008 COUNTERSHAFT is a critical rotating component within the WG 251 transmission series. This OEM genuine part serves as the primary torque-transfer interface between gear clusters, ensuring synchronized power distribution through the drivetrain. Positioned parallel to the main shaft within the transmission housing, the countershaft supports multiple gear ratios and maintains precise rotational alignment under heavy load. The SKU 4646.108.008 is manufactured to ZF’s exacting tolerances, featuring hardened bearing journals and precision-ground gear seats. When installed alongside the 4646101072: TRANSMISSION HOUSING, this countershaft forms the backbone of the gear train, directly influencing shift quality and torque capacity.
Symptoms of Failure
- Gear grinding or hard shifting: Worn countershaft splines or bearing surfaces cause misalignment, leading to audible grinding during gear engagement or resistance when moving the shift lever.
- Vibration under load: A failing countershaft produces low-frequency vibration that intensifies during acceleration, often mistaken for driveline imbalance.
- Metallic debris in transmission fluid: Flaking or spalling on the countershaft’s hardened surfaces introduces ferrous particles into the oil, visible during drain intervals.
- Intermittent gear slip: As the countershaft loses its interference fit with mating gears, power delivery becomes inconsistent, particularly in higher gears.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4646.108.008 |
| Material | Case-hardened alloy steel (20MnCr5 equivalent) |
| Overall Length | 412 mm (estimated) |
| Bearing Journal Diameter | 45 mm (front) / 50 mm (rear) |
| Weight | 6.8 kg (15.0 lbs) |
| OEM Reference | ZF 4646.108.008 |
| Surface Hardness | 58-62 HRC |
| Max Torque Capacity | 2,500 Nm (estimated) |
Compatibility
This countershaft is engineered for the WG 251 series, but its design parameters allow cross-compatibility with earlier ZF WG180, WG200, and WG210 models when used with the correct 4646301201: HOUSING. It also integrates with the 4646301166: COVER assembly to seal the bearing cavity. For secure mounting, use the 0636101051: CAP SCREW kit to achieve proper clamp load. Always verify shaft end-play and gear mesh clearance when retrofitting to non-WG251 transmissions.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4646101072 | TRANSMISSION HOUSING | Encloses and supports the countershaft assembly |
| 4646301201 | HOUSING | Intermediate casing for bearing retention |
| 4646301166 | COVER | Seals the rear bearing bore |
| 0636101051 | CAP SCREW | Fastens housing components |
| 4646201018 | COVER SHEET | Gasket layer for oil containment |
| 4646301277 | SCREEN SHEET | Filter mesh for oil return passages |
| 4646201019 | COVER SHEET | Secondary sealing gasket |
| 0730365125 | TYPE PLATE | Identification tag for transmission model |
| 0631311009 | GROOVED STUD | Alignment dowel for housing mating |
| 0636010216 | HEXAGON SCREW | General fastening hardware |
