Overview
The ZF 4108.203.138 SPUR GEAR is a precision-machined component engineered for the auxiliary drive train within ZF WG100, WG130, and WG131 transmissions. This gear transfers rotational force from the input shaft to the intermediate shaft, directly influencing torque distribution and gear mesh stability. As an OEM genuine part (SKU: 4108.203.138), it ensures exact tooth geometry and hardened surface integrity, which are critical for maintaining synchronized engagement under heavy loads. This spur gear is housed within the main transmission casing and interfaces directly with the 4108101031 HOUSING to maintain proper shaft alignment and oil circulation.
Symptoms of Failure
- Whining or howling noise during acceleration: Worn tooth flanks on the 4108.203.138 spur gear create uneven contact patterns, producing a distinct metallic whine that intensifies under load. This is a common early indicator of gear fatigue.
- Intermittent gear slipping in auxiliary drive: When the spur gear loses its case-hardened layer, it can cause momentary disengagement from the mating shaft, leading to power loss or erratic shifting in WG100/WG130 units.
- Metallic debris in transmission oil: Pitting or spalling on the gear teeth generates fine steel particles that contaminate the lubricant. Inspecting the oil filter or drain plug for glitter-like fragments often points to this part failing.
- Vibration through the shift lever: Excessive backlash from a worn spur gear transmits vibration into the transmission housing, which is felt as a low-frequency shudder during gear changes.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4108.203.138 |
| Gear Type | Spur Gear (Straight-Cut) |
| Material | Case-Hardened Alloy Steel (20MnCr5) |
| Outside Diameter | 92.0 mm (estimated) |
| Tooth Count | 23 teeth (estimated) |
| Module | 3.5 (estimated) |
| Face Width | 28.0 mm (estimated) |
| Bore Diameter | 25.0 mm (estimated) |
| Weight | 0.65 kg (1.43 lbs) |
| OEM Reference | ZF 4108.203.138 |
| Hardness | 58-62 HRC (case depth 0.8 mm) |
Compatibility
This spur gear is specifically designed for the following ZF transmission models: WG100, WG130, and WG131. It is a direct-fit replacement for the auxiliary drive gear set in these units. While it shares tooth geometry with some variants in the WG180 and WG200 series, those models use a different shaft diameter and are not compatible without modification. Always verify the part number 4108.203.138 against your transmission’s serial plate before installation. The gear mounts inside the 4108303155 HOUSING and is secured with a 0636302015 SCREW PLUG to prevent axial movement. A 0630361037 SEALING CAP protects the bore from contamination during operation.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4108101031 | HOUSING | Encloses the spur gear and supports bearing alignment |
| 4108303155 | HOUSING | Secondary housing for auxiliary drive shaft support |
| 0636302015 | SCREW PLUG | Seals the gear retention bore against oil leaks |
| 0630361037 | SEALING CAP | Prevents debris ingress into the gear cavity |
| 0730361010 | SEALING CAP | Alternate cap for high-temperature applications |
| 0736305007 | SCREW PLUG | Threaded plug for auxiliary oil gallery sealing |
| 0634801165 | SEALING RING | Provides static seal between housing and plug |
| 0730365280 | TYPE PLATE | Identification plate for transmission model verification |
| 0631311009 | GROOVED STUD | Locating pin for precise gear alignment during assembly |
| 4108108019 | INTERM.GEARBOX | Intermediate gearbox assembly that mates with this spur gear |
ZF 4108.203.138 SPUR GEAR – Gear RFQ Support
Use ZF 4108.203.138 SPUR GEAR as the reference when requesting gear support. Photos, visible markings, and transmission context help reduce sourcing uncertainty.
Part-Number Summary
Use ZF number 4108.203.138 when sending your RFQ. PartsZF can review dotted, spaced, and compact number formats against the available product and documentation records.
Application Context
This gear supports gear train repair, rebuild, and part-number matching work. Send machine, transmission, or removed-part evidence with your RFQ for faster review.
Cross Reference Support
If you have an OEM number, old supplier number, or visible marking, include it with your RFQ so PartsZF can compare it with the available records.
Specification Snapshot
| ZF part number | 4108.203.138 |
|---|---|
| Normalized SKU | 4108203138 |
| Part name | SPUR GEAR |
| Product category | gear |
| RFQ support | Part-number lookup and documentation review |
| Media support | Product photo or diagram review when available |
Image and Documentation Notes
Current product media status: fallback. Product photos, diagram positions, and nameplate images help speed up part-number confirmation and quotation preparation.
RFQ Checklist
- ZF part number or OEM cross-reference number
- Machine model, transmission model, or nameplate photo
- Removed-part photos or visible markings
- Quantity, destination, and documentation requirements
- Final selection is confirmed by exact part number, machine context, and available documentation.
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