How to Identify a Ring and Pinion

by Jennifer Simon
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gear device image by Pali A from

The ring and pinion gear set, used to increase torque and power output in all-wheel-drive vehicles, is easily identifiable by its unique shape. The pinion, a bolt-shaped piece with a flared head at one end, fits onto the ring, a simple circle, with a series of meshed crescent-shaped teeth. While all ring and pinion sets are similar in design, they appear in a variety of ratios with many subtle differences depending on their manufacturer, and can be difficult to tell apart. Changing these parts to adjust the ratio is one of the simplest ways to increase performance in a vehicle.

Manufacturers' Codes

Step 1

Separate the ring gear from the pinion, so that it is easily inspected. Every manufacturer has a unique series of letters and numbers that refers to each specific part they produce.

Step 2

Identify and transcribe the manufacturer's code imprinted on the ring gear. This will be a long string of letters and numbers without any clear meaning. For example, a 1969 Camaro might have the code "1 GM 3998234 17 49 2.56 4 69" etched into the gear.

Use catalogs from parts/vehicle manufacturers to match the code to a specific part set. In the example of the Camaro (GM 3998234 17 49 2.56 4 69), you'll find that "1" correlates to "Chevrolet," "GM" is for the producer, General Motors, "3998234" is the part number, "17" is the number of pinion teeth, "49" is the number of teeth on the ring gear, "2.56" is the ratio between gears, and "4 69" is the month and year it was produced - in this case, April of 1969. These are just some examples, and the real codes could relate other information, depending on the manufacturer, such as where the part was manufactured.

Measurement and Ratio

Step 1

Separate the ring gear and pinion so that you are able to measure them. In cases where the manufacturers' codes are no longer legible, you will need to determine the physical measurements of both the ring gear and pinion, as well as the ratio between them.

Step 2

Use calipers to measure both ring and pinion diameters to a tenth of an inch. Count the teeth on both the ring gear and pinion. To determine the ratio between the gears, divide the number of teeth on the pinion by the number of teeth on the ring.

Use your measurements with manufacturers' catalogs to find part sets that match. The size and ratio between ring and pinion are often unique to a single part set, and can be used to search for a manufacturer when the stamped code isn't clear.

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