This information is in addition to the "Tires" portion located in Section 5 of your owner manual.
When tires are changed from the original equipment size to those adapted to railroad track gage, the Vehicle Control Module (VCM) must be reprogrammed to correct the speedometer reading.
Truck Models C/K 2500: LQ4 6.0 L V8 Engine and MT1 4L80-E Automatic Transmission. The transmission calibration part numbers are as follows:GT4 Axle | 12578772 |
GT5 Axle | 12578773 |
Reprogramming the VCM is done with a TECH II electronic diagnostic system. Your GM truck dealer has this equipment. Your dealer has the correct calibration identified by the calibration part numbers on the following chart and any later updates after this publication.
New Tire Size | Axle Code | Calibration Part Number |
|---|---|---|
8-19.5 Custom Xtra/Super High Miler 593 Rev per Mile (368 Rev per Kilometer) | GT4 (3.73:1) GT5 (4.10:1) | 12583798 12583799 |
8R19.5 Vandura Commercial/School Motor Home Chassis 608 Rev per Mile (378 Rev per Kilometer) | GT4 GT5 | 12583800 12583801 |
G133 Unisteel 8R19.5 626 Rev per Mile (389 Rev per Kilometer) | GT4 GT5 | 12583802 12583803 |
Please refer to the light duty series GM BODY BUILDER BOOK for further general information regarding vehicle modification. | ||
