What cars did the 8.5 rear end come in?
The 8.5-inch rear end was used across a broad range of Ford-family vehicles, spanning the late 1960s through the early 1990s, including many full-size and mid-size cars and some light trucks. It’s a Ford-produced 8.5-inch ring-gear axle that was gradually superseded by the stronger 8.8-inch unit in later years.
Exact year-by-model usage varied by market, trim, and production run. To confirm whether a specific car used the 8.5" rear end, check the axle code on the axle tag or consult the vehicle’s factory service manual for that year and model.
Common passenger-car applications
Here are several passenger-car platforms and lineups in which the 8.5" rear end is frequently cited in guides and user references. Not every year and trim used this axle, so verification is essential for a precise match.
- Ford Fairlane and Mercury Comet (late 1960s to mid-1970s)
- Ford Torino and Mercury Montego (late 1960s to mid-1970s)
- Ford Mustang II platform vehicles (1974–1978)
- Ford LTD and Mercury Grand Marquis (late 1960s to early 1990s)
- Ford Crown Victoria and certain Lincoln/Mercury luxury variants (late 1980s to early 1990s, depending on market and trim)
These examples reflect commonly cited usage in manuals and repair literature; there were exceptions and regional variations. Always verify with the vehicle’s axle code and service documentation.
Axle identification tips
To confirm a car’s axle, look for stamping on the axle tube or tag that identifies the axle type, gear ratio, or ring-gear diameter. The 8.5" designation is the key clue, but some models used multiple rear-end options within a generation.
Common truck and van applications
In trucks and vans, the 8.5" rear end appeared in certain light-duty configurations where Ford used the 8.5" family alongside other axles. Availability varied by year, model, and market, and some vans and trucks shifted to other rear ends for strength or packaging reasons.
- Ford F-Series (light-duty pickups) — select years and trims during the late 1960s–1980s
- Ford Econoline vans — several early-generation configurations
- Mercury/Lincoln commercial or utility variants — region-specific and model-specific
As with passenger cars, axle codes and build sheets are your best sources for definitive confirmation of the 8.5" rear end in a given vehicle.
Interchange and compatibility notes
Part interchange can be tricky because Ford offered many axles with overlapping gear ratios and spline counts. If you’re swapping in or out an 8.5", consult the exact model-year service manuals and cross-reference axle suffix codes. Aftermarket catalogs and Ford’s own parts guides can help verify compatibility for gear ratios, spline counts, and mounting patterns.
How to identify an 8.5" axle
Identification typically starts with checking the axle code on the tag near the differential or on the axle housing. Measuring the ring gear diameter (8.5 inches) and counting the spline count (often 28- or 30-spline variants) provides clues. Reference the vehicle’s production brochure or a factory service manual to tie the code to a specific year/model.
Why this matters for restoration and repairs
Knowing whether a car uses the 8.5" axle matters for parts availability, gear ratios, and compatibility with suspension and brake components. While the 8.5" is less common today than the later 8.8", it remains well-documented in vintage Ford catalogs and aftermarket sources, making restoration and swaps feasible with proper verification.
Summary
The Ford 8.5-inch rear end appeared across a broad slice of Ford, Mercury, and Lincoln passenger cars from roughly the late 1960s through the early 1990s, and it also showed up in some light-truck and van configurations. If you’re researching a specific vehicle, share the exact year, model, and market, and I can pinpoint the precise axle option and provide guidance on identification and parts availability. Overall, the 8.5" axle was widespread among Ford’s lineup in its era, before being progressively supplanted by stronger rear-end designs.
How do you tell if I have a 8.2 or 8.5 rear end?
And you can see there is no ears on the bottom. It's just plain this is an 8.2 in ring gear that's an 8.8 uh 8.5. That's a stronger rear end than this one. So that's the explanation between an 8.5.
What did the 8.5-10 bolt come in?
The 8.5-inch 10-bolt rearend was used in cars and trucks over a wide range of years. It first appeared in 1970 production cars as a corporate replacement for the 8.2-inch 10-bolt rearend. It was used in different models by all GM divisions – except for Cadillac.
How do you tell if you have a 7.5 or 8.5 rear end?
You can tell the difference between a 7.5 and 8.5 rear end by looking at the shape of the cover, the shape of the axle tubes, and the protrusions on the bottom of the housing. The 8.5 has a round cover with larger, rectangular protrusions at the bottom, while the 7.5 has a more squared or oval cover with smaller, crescent-shaped lugs at the bottom. Additionally, the axle tubes on an 8.5 are flared or stepped down as they enter the pumpkin, while the 7.5 has straight axle tubes.
This video shows how to visually identify a GM 10 bolt rear axle, including how to distinguish between a 7.5 and 8.5 rear end: 53sandhotrodshopYouTube · Dec 14, 2023
Visual differences
- Cover shape: An 8.5 has a round rear cover, whereas the 7.5 has a more squared-off or oval cover.
- Axle tubes: The tubes on an 8.5 will appear to swell or flare out just before entering the differential housing. The 7.5 has straight axle tubes.
- Bottom protrusions: The 8.5 has larger, rectangular "ears" or protrusions at the bottom of the housing (around the 5 and 7 o'clock positions). The 7.5's protrusions are smaller and more crescent-shaped.
Other methods
- Measure the bolts: On some GM 10-bolt rears, the distance between the bottom center bolt and the nearest bolt on either side can be used for identification.
- 8.5: The distance is approximately 3.753.753.75 inches.
- 7.5: The distance is approximately 3.253.253.25 inches.
- Check the vehicle's RPO codes: Look for a sticker in the driver's side doorjamb or glove box. The codes listed under "Axle" or "RPO" will specify the factory-installed rear end. This is the most accurate method if the rear end is original.
What vehicles came with 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.
