Speedometer Calibration Test

Speedometer accuracy can be checked by timing the vehicle on a measured mile and performing the following test.
1. Time the number of seconds it takes to travel one measured mile at an indicated 10, 30, and 60 mph.
2. Calculate the vehicle speed using the following formula:
- mph = 3600 divided by seconds.
3. Acceptable ranges are:
- 16.1 Km/h (10 mph) in 345-275 seconds.
- 48.3 Km/h (30 mph) in 115-125 seconds.
- 96.5 Km/h (60 mph) in 57-62 seconds.

NOTE: The Ford Speedo Gear Supplement Charts in the Ford Master Parts Catalog show the proper speedometer gears to use for various rear axle and tire size OEM combinations.