What is the final drive ratio of a Ford Sierra 2.3ltr diesel 5 speed?

There's no single final drive ratio for all Ford Sierra 2.3L diesel 5-speeds. The final drive ratio varied depending on the specific model year and even sometimes the options selected. To find the exact final drive ratio for a particular car, you'd need to:

* Check the vehicle's documentation: The owner's manual or service manual might list the final drive ratio.

* Look for a sticker or plate: Some manufacturers place a sticker with specifications, including the final drive ratio, somewhere in the engine bay or under the car.

* Inspect the differential: The differential itself might have a tag with the ratio stamped on it, but this requires removing the differential cover. This is best left to a mechanic.

* Consult a Ford parts catalog: Using the car's VIN, a Ford parts catalog (possibly accessed through a dealer) might reveal the specific ratio used in that particular vehicle's build.

Without more specific information about the year and model of the Ford Sierra 2.3L diesel 5-speed, it's impossible to give you a definitive answer.