Speedometer Calibration

Remove instrument cluster from vehicle. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Plug speedometer calibration connector from Service Kit (25085515) into back of instrument cluster, and momentarily touch calibration connector wires to battery terminals. See Fig 1 and Fig 2 .
Use vehicle axle ratio, tire size and tread type to determine appropriate pins to remove from calibration clip. Pins are numbered 1 through 8 from top (rectangular end) to bottom (tapered end). See Fig 1.
Remove pins by bending them back and forth using long needle-nose pliers. Insert modified calibration clip into 8 holes in rectangular slot on back of instrument cluster. See Fig 2. Install cluster in vehicle.

Fig 1: Identifying Speedometer Calibration Components

Courtesy of GENERAL MOTORS CORP.

Fig 2: Exploded View of Speedometer Calibration Service Kit Components & Locations

Courtesy of GENERAL MOTORS CORP.