For 1990-2009 cars

# Compensating for Different Axles Ratio and Tire Sizes with a VCI Number - keywords calibration ECM PCM pinion recalibrate reflash reprogram ring wheel TCSC techline

Subject: | Compensating for Different Axle Ratio and Tire Sizes with a VCI Number

Models: | All GM Passenger Cars

| All GM Light Duty Trucks

| with a Programmable ECM or PCM

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

### Condition/Concern:

If the rear axle ratio or tire size is changed, abnormal vehicle operation, such as harsh shifts or incorrect speedometer operation, may be experienced.

### Recommendation/Instructions:

TCSC (Techline Customer Support Center) may be able to supply a VCI number on the models below to compensate for supported axle ratio or tire size changes if they were an available combination from the factory. The new vehicle sales department may be able to determine if an axle ratio and tire size combination was available as a factory option. If the axle ratio and tire size combination was not available as a factory option, TCSC can not supply a VCI number.

#### Axle Ratio Changes are Supported on the Following Models:

• | 2002 Chevrolet Camaro

• | 2002 Pontiac Firebird

• | 2003-2005 Chevrolet Corvette

• | 1996-2005 Trucks, Vans and Utility Vehicles

#### Tire Size Changes are Supported on the Following Models:

1996-2005 Trucks, Vans and Utility

If a VCI number is needed to compensate for a supported axle ratio or tire size change, contact TCSC at 1-800-828-6860. Once connected, select Prompt 1 and then Prompt 2 for VCI numbers.

Important: TCSC can not supply a VCI number to increase the fuel cut off speed if tires with a faster speed rating are installed.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.