How wide is a 12 bolt Chevy rear end?
There isn’t a single universal width for a Chevy 12-bolt rear end. Most passenger-car 12-bolts have a wheel-track width around 60 inches, give or take a bit, depending on body style and braking setup. The exact measurement for your axle depends on the model family (A-, B-, or F-body) and whether you’re using drum or disc brakes. This article breaks down the typical ranges and explains how to measure your specific unit.
What determines the width
Width is defined by the distance between the wheel mounting surfaces (the track width) and is influenced by the axle housing shape, the type of brakes, and any aftermarket components. Different GM model families used slightly different housings, even when using the same 12-bolt designation. If you’re swapping wheels or planning a suspension upgrade, verify the exact spec for your axle to ensure proper fitment.
Typical ranges by model type
Below are general ballparks for common GM 12-bolt rear ends. Exact figures can vary by year, brake type, and whether a spacer or conversion kit is installed; always measure your unit for precision.
A-body (Chevelle/Nova with 12-bolt)
Generally around 58.5–60.5 inches track width. This range covers drum and disc brake configurations commonly found in mid-size Chevelle and Nova variants.
B-body (Impala/Caprice with 12-bolt)
Typically about 60.0–61.5 inches track width, reflecting the wider full-size chassis used in these cars.
F-body (Camaro/Firebird with 12-bolt)
Often around 60.0–61.0 inches, depending on brakes and factory options. Some performance packages may shift width slightly wider.
Trucks and vans with 12-bolt rear ends
In GM light trucks and vans that used a 12-bolt, track width usually sits in the low-to-mid 60s inches, again with variations based on brakes and axle code.
Note: These are approximate ranges for common configurations. The exact width for a specific axle is best obtained from the factory service manual, stamping codes, or measurement.
How to measure your 12-bolt width
The following steps give you the precise width of your own axle, which is the most reliable way to plan wheels and suspension modifications.
- Securely lift and support the vehicle, remove the rear wheels for clear access.
- Measure the track width by recording the distance between the inner faces of the wheel mounting surfaces (the hub-to-hub line across the axle).
- Record the measurement in inches. Repeat on the other side to verify symmetry.
- Note any spacers, aftermarket brakes, or adapters that may affect the width.
- If you prefer a centerline measurement, measure from the center of one axle tube to the center of the opposite tube across the housing.
- Consult your vehicle’s service manual or GM axle data for exact spec if you plan a precise swap or wheel fitment.
Measuring in this way yields the exact figure you need for wheel fitment, suspension clearances, and ensuring compatibility with aftermarket parts.
Where to find exact specs for your axle
To obtain the official spec for your exact axle, use these sources:
- Factory service manuals for your year and model (look up the track width or axle type).
- GM axle specification sheets and documentation for 12-bolt configurations.
- Trusted online databases that catalog GM rear-axle dimensions by model and year.
- Stamping codes on the differential housing (axle code) that correspond to a published spec.
When upgrading wheels or suspensions, use the measured width rather than relying on general ranges to ensure proper clearance and steering geometry.
Summary
The Chevy 12-bolt rear end does not have a single fixed width. In practice, most passenger-car GM 12-bolts sit in a narrow band around 58.5–61.5 inches track width, depending on the model family (A-, B-, or F-body) and braking setup. The only reliable way to know your axle’s width is to measure it directly or consult the exact GM factory spec for your year and model. With the measured width, you can select wheels, brakes, and suspension components that fit correctly and perform as intended.
Are all GM 12 bolt rear ends the same?
Are All GM 12-Bolt Rear Ends the Same? Not even a little. There were car GM 12-bolt axles and truck versions, and nothing interchanges between the two versions. There are housing differences in each version as well, depending on the year and model they were installed in.
What is the width of the 1969 Camaro 12 bolt rear end?
60 inch is stock width.
How wide is a #12 bolt?
US Screw Size Conversion Chart
| Screw Size | Inch Decimal | Metric Equivalent |
|---|---|---|
| #6 | 0.138 in. | 3.51 mm |
| #8 | 0.164 in. | 4.17 mm |
| #10 | 0.190 in. | 4.83 mm |
| #12 | 0.216 in. | 5.49 mm |
How wide is the rear end of a Chevelle?
The width of a Chevelle rear end varies by year: 1964–1967 models are approximately 60 inches wide (wheel mounting surface to wheel mounting surface), while 1968–1972 models are approximately 61.25 inches wide. The specific measurement for 1964-1967 is sometimes listed as 60 inches or 60 and a quarter inches, while the 1968-1972 is listed as 61 and a quarter inches.
- 1964–1967: ~60 inches (sometimes cited as 60.25 inches)
- 1968–1972: ~61.25 inches
