What gear ratio does a 1987 mustang with 5.0 automatic have?

There's no single answer to what gear ratio a 1987 Mustang 5.0L with an automatic transmission had. The ratio depended on several factors including the specific rear axle installed at the factory. Ford offered several options. To find the correct ratio for *your* specific car, you need to:

* Check the Vehicle Identification Number (VIN): The VIN can sometimes help decode the original specifications, but this information isn't always consistently recorded.

* Look at the axle tag: The differential housing (rear axle) usually has a tag affixed to it with the gear ratio printed on it. This is the most reliable method.

* Inspect the differential: If the axle tag is missing or illegible, you can count the teeth on the ring gear and pinion gear, then divide the ring gear teeth by the pinion gear teeth to calculate the gear ratio. This requires removing the differential cover (at your own risk) and some knowledge of differentials.

Without this information, it's impossible to tell you the gear ratio. Common ratios for that era included 2.73, 3.08, and 3.55, but others were possible.