Are all Ford 9-inch rear ends the same size?
The Ford 9-inch rear end is one of the most popular and versatile rear axle assemblies in the automotive world, especially among hot rodders, racers, and classic car enthusiasts. However, a common question arises: Are all Ford 9-inch rear ends the same size? The answer is no, and here's why.
Understanding the Ford 9-Inch Rear End
The Ford 9-inch rear end was introduced in 1957 and became a staple in Ford vehicles for decades. Its durability, ease of customization, and ability to handle high horsepower made it a favorite for performance applications. Despite its name, the "9-inch" refers to the diameter of the ring gear, not the overall size of the assembly.
Why Ford 9-Inch Rear Ends Vary in Size
While the ring gear diameter remains consistent at 9 inches, other dimensions and specifications can vary depending on the vehicle model and application. Here are the key factors that contribute to these differences:
- Axle Width: The overall width of the rear end assembly can differ based on the vehicle it was designed for. For example, a Ford truck may have a wider axle than a Mustang or a Torino.
- Housing Design: The shape and design of the axle housing can vary. Some housings are designed for leaf spring setups, while others are made for coil spring suspensions.
- Axle Shaft Length: The length of the axle shafts can differ depending on the width of the rear end and the specific vehicle application.
- Pinion Offset: The pinion gear's position relative to the centerline of the axle can vary slightly, affecting compatibility with certain vehicles.
Interchangeability and Customization
One of the reasons the Ford 9-inch is so popular is its adaptability. Many aftermarket companies produce custom housings, axles, and components to fit a wide range of vehicles and applications. This means you can modify a Ford 9-inch rear end to suit your specific needs, whether you're building a drag racer, off-road truck, or classic street car.
How to Identify the Right Ford 9-Inch for Your Vehicle
If you're considering using a Ford 9-inch rear end for your project, here are some tips to ensure you get the right fit:
- Measure Your Vehicle's Requirements: Determine the correct axle width, suspension type, and pinion offset for your vehicle.
- Check the Tag or Casting Numbers: Original Ford 9-inch rear ends often have tags or casting numbers that can help identify their original application.
- Consult with Experts: If you're unsure, consult with a professional or an experienced shop specializing in rear end setups.
Conclusion
While all Ford 9-inch rear ends share the same ring gear diameter, they are not all the same size. Variations in axle width, housing design, and other factors make it essential to choose the right configuration for your specific vehicle and application. With proper research and customization, the Ford 9-inch remains one of the most versatile and reliable rear ends available.
Frequently Asked Questions
How much horsepower can a Ford 9 inch rear end hold?
"They're good only to 400hp max," says Tom at Tom's Differentials. "Anything above that should use today's beefed-up, redesigned, nodular-iron aftermarket cases. They're good to 800 hp, if built properly. The next step beyond that would be the high end, completely redesigned, Mark Williams billet-aluminum housing.
How wide is the Ford 9 inch rear end?
These axles are 65 inches wide from wheel mounting surface to wheel mounting surface (a 68-inch-wide E-series van version is also common), feature the legendary 9-inch diameter ring gear, large Timken set 20 axle bearings, semi-floating 28- or 31-spline axleshafts, drum brakes, and a 5-on-5.5 lug pattern.
How to tell the difference between Ford 8.8 and 9.75 rear end?
On the passenger's side upper and lower corners, there's two semi-circular divots that can easily be seen when looking at the cover from straight on. While the Super 8.8's cover has a bulge for the ring gear, it's not anywhere near as pronounced as the 9.75's.
When did Ford stop using the 9 inch rear end?
1986
The Ford 9-inch is an automobile axle manufactured by Ford Motor Company. It is known as one of the most popular axles in automotive history. It was introduced in 1957 model year cars and ended production in 1986, having been phased out in favor of the Ford 8.8 inch axle.
What is the strongest Ford rear end?
What Makes the 9-inch Ford Rearend So Great? From the archives: Legendary tech guru Marlan Davis explains why the 9-inch Ford is the strongest rearend out there—it's all due to “hypoid distance.”
What is so special about a Ford 9 inch rear end?
Unlike most rear differentials that rely on two bearings to support the pinion gear, the Ford 9-inch employs a three-bearing system. This additional support provides several technical and performance advantages, particularly in high-stress and high-torque applications.
How do I know what Ford 9 inch rear end I have?
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. If the socket fits (as shown in our photo below) it is a Ford 8-inch housing.
Are all Ford 9-inch rear ends the same?
We should point out there are three distinct 9-inch axle ends: the late big bearing (Torino) and the early big bearing both take a 3.150-inch od wheel bearing (the difference is in the bolt spacing for the backing plates), the small bearing ends take a 2.834 od bearing with yet a different backing plate bolt pattern.
How do I identify my Ford rear differential?
The most accurate differential identification is provided by the bottom line of the tag number or axle tube stamp. Differential tags can easily be used to identify Dana and Ford differentials.
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.
