Overview
The ZF 0501.331.874 OIL SIGHT GLASS is a critical visual diagnostic component installed in the upper casing of ZF powershift transmissions used in heavy construction machinery. This OEM genuine part allows operators and maintenance technicians to quickly verify the transmission fluid level and condition without opening the housing. The SKU 0501.331.874 is precision-engineered to withstand high thermal cycling and vibration common in excavators and wheel loaders. When inspecting the driveline, always check the condition of the 2098109042 DIFFERENTIAL and the 2098309011 CROWN WHEEL for matching wear patterns, as oil starvation from a failed sight glass can accelerate damage to these internal components.
Symptoms of Failure
- Transmission fluid seepage around the sight glass window – A common sign of a degraded O-ring or cracked polyamide lens, leading to gradual oil loss and potential contamination of the clutch packs.
- Cloudy or opaque viewing window – Internal chemical attack or thermal degradation of the glass material prevents accurate fluid level checks, risking low-lubrication conditions.
- Intermittent gear engagement hesitation – When the sight glass fails completely, air ingestion into the hydraulic circuit can cause spongy clutch response and delayed shifts under load.
- Visible oil film on the transmission housing exterior – A weeping sight glass often leaves a distinct oil trail below the mounting boss, indicating the seal has lost its elasticity.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 0501.331.874 |
| Material | Polyamide lens with nitrile rubber O-ring |
| Thread Size | M22 x 1.5 |
| Overall Diameter | 30 mm |
| Weight | 0.04 kg |
| OEM Reference | ZF 0501.331.874 |
| Max Operating Temp | 120°C (248°F) |
Compatibility
This oil sight glass is designed for ZF powershift transmissions commonly found in construction machinery, including the WG180, WG200, and WG210 series. It also fits select 4WG-200 and 6WG-200 models used in articulated dump trucks and graders. When replacing this part, it is recommended to also inspect the 2099209001 DIFFERENTIAL and the 2098309010 DIFFERENTIAL HOUSING for any signs of oil contamination or metal debris that may have entered through a compromised sight glass.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 2098109042 | DIFFERENTIAL | Distributes torque between drive wheels |
| 2098309011 | CROWN WHEEL | Transfers rotational force from pinion to differential |
| 2099209001 | DIFFERENTIAL | Rear axle torque distribution assembly |
| 2098309010 | DIFFERENTIAL HOUSING | Encloses differential gear set |
| 2098309009 | DIFFERENTIAL HOUSING | Front axle housing for gear protection |
| 2098309031 | AXLE BEVEL GEAR | Changes drive angle in axle assembly |
| 2098309030 | AXLE BEVEL GEAR | Matching bevel gear for torque transfer |
| 2098309032 | DIFFERENTIAL BEVEL GEAR | Planetary gear within differential carrier |
| 12883200682 | THRUST WASHER | Reduces axial friction in gear sets |
| 0635332059 | BALL BEARING | Supports rotating shafts with minimal friction |
