You primarily measure a ring gear by its diameter across the face of the gear. Here's a breakdown of the methods:
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Direct Measurement:
- Using a Tape Measure: The simplest method is to place a tape measure directly across the face of the ring gear to determine its diameter. This provides a quick and relatively accurate measurement. Note that accuracy can be affected by obstructions if the gear is still installed.
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Indirect Measurement (When Direct Measurement is Difficult):
- Visual Inspection and Identification: In situations where the ring gear is difficult to access (e.g., when it's still within the differential housing), you might be able to identify the differential and, therefore, the ring gear size based on other characteristics, such as the number of cover bolts. For example, many differentials are identified by the number of cover bolts.
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Things to Keep in Mind:
- Accuracy: When measuring with a tape measure, ensure the tape is taut and runs directly across the center of the gear for the most accurate reading.
- Accessibility: If the ring gear is inside the differential housing, access can be limited.
