How do I know what Chevy differential I have?
The quickest way to know what rear differential you have on a Chevy is to read the axle code or gear ratio printed on the data plate or differential tag and then cross-check it with GM’s RPO (Regular Production Option) codes or your vehicle’s build sheet. If those aren’t accessible, you can determine the ratio by rotating a wheel with the driveshaft held in place, or inspect the cover for stamped or tagged information.
Where to look for codes and data
This section explains where to find official identifiers that tell you the exact differential model, ratio, and options.
- Check the driver’s door jamb data plate or the vehicle’s glove box sticker for an axle code and the stated ratio. These codes are the factory reference for your axle configuration.
- Look for a small metal tag or embossed stamping on the differential housing or cover. It may list the gear ratio (for example, a number like “3.73”) and sometimes an option code indicating a limited-slip or locking differential.
- If your vehicle has been serviced or the build sheet is preserved, pull the VIN’s build sheet or use a GM VIN decoder to get the axle/RPO code that confirms the differential type and ratio.
- If you can’t locate any codes, you can determine the ratio by safely lifting the rear end, rotating one wheel and counting how many driveshaft turns occur per wheel revolution (the ratio is driveshaft turns per wheel turn).
These steps help identify the basic axle family and gearing, which is often enough to source the correct parts or determine compatibility.
Read the differential tag or cover stamping
The tag or stamping on the differential is typically the most reliable source for exact gearing and option data.
- Inspect the differential cover for a stamped number or a small plate affixed to the cover. The stamping may show the gear ratio (for example, 3.73, 2.73) and sometimes an option code indicating LSD or other features.
- Look for an identifier such as a G80 badge or an option code on the tag, which signals a locking differential or other performance feature.
- On some models, the tag is a separate metal plate bolted to the cover or along the axle housing; note all numbers and letters exactly as stamped.
- When in doubt, record the numbers and cross-reference them with GM’s published RPO lists or service literature to confirm the differential type.
The cover tag and any stamped codes are generally the clearest way to verify the exact gearing and whether a limited-slip or locker is installed.
Use the VIN or build sheet to confirm
If the direct axle codes are missing or unreadable, your best bet is to recover the factory configuration from the VIN or the build sheet.
- Retrieve the VIN from the driver’s side dashboard display or door sticker.
- Enter the VIN into a GM VIN decoder or check the vehicle’s build sheet to pull the axle/RPO codes and the specified gear ratio.
- Cross-check the extracted axle information with GM’s official RPO code documentation to confirm the differential type (open, LSD, or locker) and the exact ratio.
- If you have service records, review them for references to the axle code, ratio, or locker option that was installed at the factory or by a dealer.
Using the VIN or build sheet provides a definitive answer but requires access to the VIN and a reliable decoder or build documentation.
Visual clues and common families
When you can’t access data plates or VINs, some visual cues and knowledge of common GM axle families can help you approximate what you have. Use these clues as a guide rather than a final authority.
Common rear-axle families found in Chevys
GM has used several rear-axle families across generations. Key distinctions include general size, cover design, and availability of limited-slip or locking differentials. While exact models vary by year and trim, recognizing the general family helps in sourcing parts and understanding maintenance needs.
- Smaller 7.5" and 7.875" rear axles were common on many mid- and late-20th-century Chevys, often paired with 10-bolt configurations and varying gear ratios.
- 8.5" 10-bolt axles are widely seen on many Camaros, Novas, mid-size Chevys, and some pickups from various eras, and they commonly offer options for LSD in certain packages.
- Some trucks and vans used larger 8.6" or 8.875" gear housings with different brake arrangements and a broader range of gears, including heavier‑duty LSD/locker options in certain trims.
- Older performance models can feature a 12-bolt differential, which is denser and typically found in classic muscle cars or delimited high-performance variants.
Visual clues can point you in the right direction, but the exact ratio and option (open vs. LSD/locker) are best verified through codes or direct tagging.
Practical tips and safety
Getting the correct differential information is important for maintenance, repairs, and upgrades. Follow these practical steps to stay safe and accurate.
- Work on a stable, chocked vehicle and use proper lifting equipment if you plan to inspect the axle or wheel areas.
- If you’re unsure about handling the differential or removing the cover, consult a professional tech or a qualified shop.
- Keep a photo log of any data plates or tags you inspect so you can reference the exact codes when cross-checking with GM documentation.
Following safe practices and documentary references ensures you identify the right differential without damage or misidentification.
Summary
To know exactly which Chevy differential you have, start with the data plate or axle tag to read the gear ratio and option codes, then cross-check with GM’s RPO lists or your VIN/build sheet. If codes are missing, verify by measuring the gear ratio carefully or inspecting the tag on the differential cover. Visual clues can help guide you, but the official codes and verification through a VIN decode provide the most reliable answer. When in doubt, consult a professional to confirm your axle configuration and ensure you source compatible parts.
Does the VIN number tell you the gear ratio?
You may be able to tell the gear ratio from a vehicle's VIN by using an online VIN decoder, though not all manufacturers include this information in the VIN itself. If the gear ratio is included, it will likely be in the Vehicle Descriptor Section (VDS), which are the 4th through 8th digits of the VIN. For many vehicles, a sticker on the driver's side door jamb or on the vehicle's build sheet or owner's manual is a more reliable way to find the gear ratio.
How to check the VIN
- Use an online VIN decoder: Enter the full VIN into a free online decoder. Some manufacturers have their own decoders, such as Mopar's decoder.
- Look for the gear ratio code: Some VINs will have a code within the VDS that represents the gear ratio (e.g., "3731").
- Consult the manufacturer: If the VIN decoder doesn't provide the information, contact the vehicle manufacturer for assistance.
Other methods to find the gear ratio
- Check the vehicle sticker: Look for a sticker on the driver's side door jamb or on the vehicle's build sheet. This sticker often contains detailed information about the vehicle's equipment, including the axle ratio.
- Look at the differential: Some differentials have a metal tag with the gear ratio stamped on them, or there may be a sticker on the axle itself.
- Consult your owner's manual: The owner's manual or other paperwork from the vehicle's purchase often lists the gear ratio.
How do you tell what type of differential you have?
The most accurate differential identification is provided by the bottom line of the tag number or axle tube stamp.
How do I know if I have a 3.73 or 4.10 gear?
And since we live in the day and age of 2025. Uh if you're curious. You can easily. Google you know uh the number of teeth on a ring gear.
How to tell what differential you have on a Chevy?
Information about Differentials in GM vehicles can usually be obtained by looking at the RPO or “Regular Production Option” codes contained in the Service Parts Identification tag in the glovebox or the driver's side door jamb (B-Pillar).
