How to Identify an S-10 Rear End

If you are working on a Chevrolet S-10 or planning to buy a used Chevy truck, it is important to know how to identify the rear end. The rear end of a vehicle plays a crucial role in the overall performance and drivability.

Identifying the rear end will not only help you determine its compatibility with other parts but also ensure that you have the right gear ratio for your needs. In this article, we will guide you through the process of identifying an S-10 rear end step by step.

1. Look for the S-10 Rear End Tag

The first step in identifying an S-10 rear end is to locate the rear end tag. The tag is typically found on the axle housing and contains important information such as the gear ratio and manufacturing date. It will also have the S-10 model number, which can be used to cross-reference with other sources. Additionally, look for the manufacturer’s name on the tag, as it can provide further clarity.

2. Measure the Axle Tube Diameter

Next, measure the axle tube diameter of the rear end. The S-10 rear end has different axle tube diameters depending on the year and model:

  • 7.5-inch axle tube diameter
  • 7.625-inch axle tube diameter
  • 8.5-inch axle tube diameter

Use a caliper or a measuring tape to accurately measure the diameter and compare it with these values to determine which size you have.

3. Count the Number of Cover Bolts

Now, count the number of cover bolts on the rear end. The cover bolts hold the differential cover in place. Depending on the specific S-10 model, there are three common options:

  • 10 cover bolts
  • 12 cover bolts
  • 14 cover bolts

By visually inspecting the rear end cover, you can easily count the number of bolts and narrow down the options.

4. Check the Bolt Pattern

The bolt pattern refers to the number of bolt holes on the rear end’s wheel hub. To identify an S-10 rear end, measure the distance between two adjacent bolt holes. The most common bolt patterns for S-10 rear ends are:

  • 5 x 4.75-inch bolt pattern
  • 5 x 5-inch bolt pattern

Comparing the measured distance with these values will give you a clear indication of the bolt pattern.

5. Look at the Shape of the Rear End Cover

The shape of the rear end cover is another distinguishing feature of an S-10 rear end. By observing its shape, you can further narrow down your identification. There are two common shapes:

  • Hexagon: Some S-10 rear ends have a cover shaped like a hexagon.
  • Octagon: Other S-10 rear ends have a cover shaped like an octagon.

Analyzing the shape will provide additional confirmation in identifying your S-10 rear end.

6. Check the Axle Shaft Spline Count

To continue your identification process, count the number of splines on the axle shaft. The spline count determines how many teeth or ridges there are on the shaft and is crucial when selecting replacement parts or upgrading to a higher performance axle. Common options for S-10 rear ends include:

  • 26-spline count
  • 28-spline count

Inspecting the axle shaft closely will allow you to identify its spline count accurately.

7. Measure the Distance Between the Wheel Mounting Surfaces

By measuring this distance, you can determine which specific model of S-10 rear end you have. The distance between the wheel mounting surfaces directly affects your vehicle’s track width and overall stability. For S-10 rear ends, there are two typical measurements to consider:

  • 60.5-inch distance between the wheel mounting surfaces
  • 62.5-inch distance between the wheel mounting surfaces

Using a measuring tape, measure the distance accurately and match it to the corresponding specification.

8. Look for the S-10 Rear End Casting Number

Another method to identify an S-10 rear end is by locating the casting number on the axle housing. The casting number provides valuable information about the manufacturer, gear ratio, and S-10 model variation. It is usually found near the axle tube or differential cover. Take note of this number as it can be used for future reference or when searching for replacement parts.

9. Check the Gear Ratio

The gear ratio determines the speed and power characteristics of your vehicle. To identify an S-10 rear end’s gear ratio, refer back to the rear end tag or casting number you located earlier. Common gear ratios for S-10 rear ends include:

  • 2.73 gear ratio
  • 3.08 gear ratio
  • 3.42 gear ratio

Ensure that you have accurate information on your specific rear end to make informed decisions when modifying or repairing your vehicle.

10. Look for the S-10 Rear End Identification Sticker

Finally, check for the S-10 rear end identification sticker. This sticker is typically located on the driver’s side door jamb and contains important information, including the S-10 model number, gear ratio, and manufacturer’s name. The sticker not only serves as an additional confirmation but also provides a quick reference point for identifying your rear end without relying on other sources.


Identifying an S-10 rear end is crucial for finding compatible parts and optimizing your vehicle’s performance. By following these steps and conducting a visual inspection, you can confidently determine which model of S-10 rear end you have. Remember to refer to reliable sources and cross-check information to ensure accuracy. Armed with this knowledge, you can proceed with confidence when working on or purchasing an S-10 truck.

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