What is a Mopar 8 3 4 rear end?
The Mopar 8‑3/4 rear end is Chrysler’s famous 8.75-inch ring‑gear differential, a heavy-duty rear axle used on many Mopar muscle cars from the 1960s through the 1980s. It’s renowned for strength, ease of gear changes via a removable third member, and widespread availability of performance parts. In short: it’s the durable, authentic choice for classic Mopar builds and high‑performance swaps.
What it is and why it mattered
The 8‑3/4 rear end refers to a cast‑iron housing with an 8.75-inch ring gear diameter. It features a removable carrier (the third member) that houses the differential and gears, allowing easier gear ratio changes without rebuilding the entire axle. Mopar offered this rear in open and Sure‑Grip (limited‑slip) configurations, making it a flexible platform for both daily driving and performance applications. Its robust construction and availability across numerous Mopar A‑, B‑ and E‑body models helped establish it as a benchmark for durability in the era’s high‑horsepower cars.
Key attributes of the 8‑3/4 rear end include a strong, heavy cast‑iron housing, compatibility with a wide range of factory and aftermarket gear sets, and the option of a sure‑grip/posi differential for improved traction. Over the decades, enthusiasts have relied on it not only for authenticity in restorations but also for upgrades to withstand higher horsepower in drag racing and modern performance driving.
To understand why this rear end has endured in popular culture, it helps to know its core specifications and common configurations. The following list summarizes the most important points.
Here are the core features that define the Mopar 8‑3/4 rear end:
- 8.75‑inch ring gear diameter, which contributes to overall strength and durability
- Removable third member (carrier) for easier gear ratio changes and maintenance
- Available in open or Sure‑Grip (limited‑slip) differential configurations
- Cast‑iron housing designed to fit a wide range of Mopar platforms and wheelbases
- Factory gear ratios commonly ranging from about 3.23 up to 4.56, with variations by model year and application
These characteristics helped the 8‑3/4 become a go‑to drivetrain for enthusiasts seeking both authentic Mopar flavor and real‑world strength, especially in street and strip contexts.
Who used it and what to expect today
Chrysler’s performance and muscle cars from the 1960s through the 1980s—models like the Barracuda, Challenger, Charger, Road Runner, GTX, and various B‑, E‑, and early C‑body designs—rely on the 8‑3/4 rear for its robustness. Over time, the setup has remained popular with restorers and racers because it’s well understood, widely serviced, and supported by a large aftermarket ecosystem.
Today, the 8‑3/4 remains a common target for authenticity builds and for horsepower‑focused swaps. For those upgrading or maintaining one, several paths are typical: stock replacements, performance gear‑set swaps, and aftermarket third‑member or axle upgrades to handle more power or modern braking hardware.
Common specs and compatible options
If you’re evaluating an 8‑3/4 for a project, the following outlines typical configurations you’ll encounter and practical upgrade paths.
Common gear ratios and configurations you’ll see in the wild:
- Open differential with various factory gear ratios (commonly 3.23–3.55 on lighter setups)
- Sure‑Grip/posi limited‑slip option for improved traction
- Higher‑horsepower/drag‑strip variants that use gear sets around 4.10, 4.30, or 4.56
- Multiple housing widths and axle setups to fit different Mopar platforms (A, B, E bodies)
For modern builds, enthusiasts frequently upgrade the rear with aftermarket third‑member assemblies, improved gear sets, and brake/axle conversions to accommodate disc brakes or wider tires, while preserving the characteristic Mopar look and feel.
Maintenance, upgrades and parts sourcing
Because the 8‑3/4 has been a staple for decades, parts and expertise are plentiful. Common upgrade paths include steel‑top aftermarket third members, aluminum or forged case options for certain racing applications, and high‑quality gear sets from vendors who specialize in Mopar rears. Many builders also pursue_disc brake conversions, upgraded axles, and Sure‑Grip internal components to support higher power levels and better handling in modern environments.
If you’re restoring a car or planning a swap, you’ll find robust support from specialty suppliers and a community that has documented countless installations, issues, and fixes. This makes the Mopar 8‑3/4 a practical choice for both authenticity and performance ambitions.
Summary
The Mopar 8‑3/4 rear end is a legendary Mopar differential: a heavy, 8.75‑inch ring gear rear axle with a removable carrier, offered in open and Sure‑Grip configurations, and adaptable to a wide range of Mopar bodies. Its durability, straightforward maintenance, and strong aftermarket support have made it a lasting favorite for restorations and high‑performance builds alike. Whether you’re chasing period authenticity or aiming to run digital‑age power with a classic drivetrain, the 8‑3/4 remains a foundational element of Mopar’s automotive story.
