Overview
The ZF 4123.302.001 SPEEDOMETER WORM is a precision-machined component engineered specifically for the WG150 series transmission. This OEM genuine part drives the speedometer gear train by engaging directly with the output shaft, converting rotational motion into accurate vehicle speed readings. The SKU 4123.302.001 is housed within the transmission tail housing, where it interfaces with the speed sensor assembly. For optimal alignment, this worm works in conjunction with the 4642101047: TRANSMISSION HOUSING and the 4642301207: TRANSMISSION HOUSING, ensuring precise gear mesh and signal integrity.
Symptoms of Failure
- Erratic or intermittent speedometer readings: When the worm gear teeth wear unevenly, the speed sensor loses consistent contact, causing the needle to jump or drop to zero during operation.
- Whining or grinding noise from the transmission tail section: A worn worm gear produces a distinct high-pitched whine as metal-on-metal contact increases, often mistaken for bearing failure.
- Complete loss of speedometer function: Advanced wear or tooth breakage stops the worm from driving the sensor, leaving the speedometer dead while the vehicle moves normally.
- Oil seepage around the speedometer drive housing: A degraded worm can damage the shaft seal, leading to transmission fluid leaks that worsen over time.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number | 4123.302.001 |
| Material | Case-hardened steel (carburized) |
| Weight | 0.12 kg (0.26 lbs) |
| Overall Length | 38 mm |
| Gear Diameter | 22 mm |
| Tooth Count | 8 teeth (helical) |
| OEM Reference | ZF 4123.302.001 |
| Mounting Type | Press-fit with retaining clip |
Compatibility
This speedometer worm is primarily designed for the ZF WG150 series transmission. Based on its gear geometry and shaft interface, it also fits the WG180 and WG200 models when used with the correct housing adapters. The part is not compatible with WG120 or WG250 series without modification. For proper installation, ensure the 0730365067: TYPE PLATE matches your transmission model, and secure the assembly with the 0631311009: GROOVED STUD to prevent axial movement.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4642101047 | TRANSMISSION HOUSING | Encloses the worm gear and output shaft |
| 4642301207 | TRANSMISSION HOUSING | Alternative housing for WG150 variants |
| 0730365067 | TYPE PLATE | Identifies transmission model and specs |
| 0631311009 | GROOVED STUD | Secures worm gear to output shaft |
| 4642301168 | SCREEN SHEET | Filters debris from transmission fluid |
| 4642301169 | SCREEN SHEET | Fine mesh filter for oil return line |
| 0636100621 | HEXAGON SCREW | Fastens housing cover to transmission |
| 4642301186 | SCREEN SHEET | Magnetic screen for ferrous particles |
| 4644106300 | SHIFT SYSTEM | Controls gear engagement and selection |
| 4644306500 | COVER PLATE | Seals the speedometer drive access port |
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