How do you tell if you have a 7.5 or 8.5 rear end?
When it comes to maintaining or upgrading your vehicle, understanding the specifications of your rear axle is crucial. One common question among car enthusiasts and DIY mechanics is how to determine whether their vehicle has a 7.5-inch or 8.5-inch rear end. This guide will walk you through the key differences and how to identify which one you have.
Why Does It Matter?
The size of your rear end impacts your vehicle's performance, durability, and compatibility with aftermarket parts. The 8.5-inch rear end is generally stronger and better suited for high-performance applications, while the 7.5-inch rear end is lighter and more common in standard vehicles. Knowing which one you have ensures you make the right choices for repairs, upgrades, or replacements.
Steps to Identify Your Rear End
Follow these steps to determine whether your vehicle has a 7.5-inch or 8.5-inch rear end:
- Check the Axle Code: Locate the axle code on the identification tag or sticker, typically found on the differential cover or inside the driver-side door jamb. Cross-reference the code with your vehicle's manual or an online database to determine the rear end size.
- Measure the Differential Cover: The shape and size of the differential cover can provide clues. The 7.5-inch rear end usually has a smaller, more oval-shaped cover, while the 8.5-inch rear end has a larger, more squared-off cover.
- Count the Bolts: Count the number of bolts on the differential cover. While both rear ends often have the same number of bolts, the spacing and size of the bolts can differ. Consult a guide specific to your vehicle's make and model for exact details.
- Inspect the Casting Numbers: Look for casting numbers on the axle housing or differential. These numbers can often be decoded to reveal the rear end size.
- Consult a Professional: If you're still unsure, bring your vehicle to a trusted auto repair shop. A professional mechanic can quickly identify the rear end size for you.
Common Applications of 7.5 and 8.5 Rear Ends
Understanding where these rear ends are typically used can also help you identify yours:
- 7.5-Inch Rear End: Commonly found in smaller cars and light-duty trucks. It is designed for vehicles with lower torque and horsepower requirements.
- 8.5-Inch Rear End: Often used in performance vehicles, muscle cars, and heavy-duty trucks. It is built to handle higher torque and horsepower.
Final Thoughts
Identifying whether you have a 7.5-inch or 8.5-inch rear end is an essential step in maintaining or upgrading your vehicle. By following the steps outlined above, you can confidently determine your rear end size and make informed decisions about repairs or modifications. If you’re ever in doubt, don’t hesitate to reach out to a professional mechanic for assistance.
At Kevin's Autos, we specialize in helping car owners with all their maintenance and repair needs. If you have questions about your vehicle's rear end or need expert advice, feel free to contact us. We're here to help!
Frequently Asked Questions
How to identify an 8.8 rear end?
Almost all 8.8s—and all post-1986 Ford rearends—have letters and numbers. The first number refers to the plant where it was built, and the next three refer to the ratio and type.
How can you tell the difference between a 7.5 and 8.8 rear end?
When working with a Rear Gear Set, here are a couple of things to check:
- Measure the diameter of the ring gear. A 7.5 Ring Gear will measure 7.5. An 8.8 Ring Gear will measure 8.8.
- You can also count the splines on the Pinion Gear. A 7.5 Pinion will have 28 splines & an 8.8 pinion will have 30 splines.
What cars have an 8.5 rear end?
You can find a 10-bolt 8.5-inch differential in any of these cars or trucks:
- 1970-'81 Chevrolet Camaro.
- 1970-'81 Pontiac Firebird.
- 1971-'76 Chevrolet Impala and Caprice.
- 1971-'81 Buick Centurion, Electra, Electra 225, and LeSabre.
- 1971-77 Pontiac Grand Prix.
- 1971-'77 Oldsmobile Cutlass.
How do you tell what size rear end you have?
The axle may have a sticker, and on the differential cover, you might have a small metal tag that's sticking out that will have the gear ratio stamped on it.
What Ford has a 8.8 rear end?
8.8 Solid Axle
Ford first used the 8.8 axle in 1983 model year trucks and is still in production for the Ford Ranger and Ford F-Series. It was also used in the Ford SUVs until Independent suspension replaced the solid axle.
What did the 8.5-10 bolt come in?
8.5/8.6 Housings:
The best 10-bolt, the 8.5 and later 8.6 design can be found in the following GM vehicles: 70-77 GM A-body. 70-96 B-body. 75-78 E-body.
How do I know if my rear end is 9 inch?
Ford 9 inch rear end identification is easy and can be accomplished with nothing more than a deep socket as a “go-no-go” gauge for the bottom two retaining nuts on the center section.
How do you check rear end ratio?
Number maybe try that leave one tire on on the ground and then spin your tire two full revolutions. And count your drive shaft turns. Okay so here we go you can see that I've got two pieces of tape
How do I know what rear end I have in my Chevy truck?
Identify your GMC or Chevrolet rear end gear ratio by the RPO Codes, usually located on the placard labeled “Service Parts Identification” inside the drivers door panel or glove box. Note that using the RPO code for parts identification assumes that the rear end has not been previously modified!!
How do I identify a GM 7.5 rear end?
The 7.5 rearend uses an oval cover and the housing has two small cast-in protrusions near two of the bottom cover bolts. The control arm-mounting ears on top of this 7.5 rearend denotes it is usable for any 1978-'88 GM A or G-body intermediate like a Cutlass, Monte Carlo, El Camino, Malibu, Regal, or Grand Prix.
