Comprehensive Guide: Converting a GMC Transfer Case from Full-Time to Part-Time

Introduction

GMC vehicles have been renowned for their rugged capabilities and all-wheel drive systems. However, some models, particularly those from the 1990s and early 2000s, came equipped with full-time four-wheel drive transfer cases, which can be less fuel-efficient and may not always be necessary for everyday driving. For these reasons, many owners choose to convert their transfer cases to part-time operation.

Benefits of Converting to Part-Time Transfer Case

• Increased Fuel Efficiency: By disengaging the front driveline when not needed, part-time transfer cases can significantly improve fuel economy. According to the US Environmental Protection Agency (EPA), a vehicle with a full-time four-wheel drive system can use up to 25% more fuel than a similar vehicle with a part-time system.
• Reduced Wear and Tear: Constant engagement of the front driveline in full-time four-wheel drive systems can lead to premature wear on driveline components, such as the transfer case, driveshafts, and differentials.
• Improved Handling: Part-time four-wheel drive systems provide better handling on dry pavement, as the absence of driveline binding reduces torque steer and improves steering responsiveness.

How to Convert a GMC Transfer Case from Full-Time to Part-Time

The specific steps involved in converting a GMC transfer case from full-time to part-time will vary depending on the model year and specific transfer case model. However, the general procedure is similar for most vehicles.

Materials:

• Replacement transfer case shift motor
• Socket wrench set
• Screwdriver
• Electrical tape
• RTV sealant

Instructions:

1. Safety First: Park the vehicle on a level surface, engage the parking brake, and disconnect the negative battery terminal.
2. Remove the Old Shift Motor: Locate the transfer case shift motor, which is typically situated on top of the transfer case. Disconnect the electrical connector and remove the bolts that secure the motor to the transfer case.
3. Install the New Shift Motor: Position the replacement shift motor onto the transfer case and secure it with the bolts. Reconnect the electrical connector.
4. Adjust the Linkage: In some cases, it may be necessary to adjust the transfer case linkage to ensure proper engagement and disengagement of the four-wheel drive system. Refer to the vehicle's service manual for specific instructions.
5. Seal and Test: Apply RTV sealant around the base of the shift motor to prevent water and debris from entering. Reconnect the battery and test the operation of the four-wheel drive system by shifting between 2WD and 4WD.

Common Mistakes to Avoid

• Using the Wrong Shift Motor: It is crucial to use a replacement shift motor that is specifically designed for the intended transfer case model. Using an incorrect motor can result in improper engagement or disengagement of the four-wheel drive system.
• Incorrect Linkage Adjustment: Improper adjustment of the transfer case linkage can prevent the system from engaging or disengaging properly. Always follow the vehicle's service manual for specific adjustment procedures.
• Neglecting to Seal Properly: Failure to seal the shift motor properly can allow water and debris to enter the transfer case, leading to potential damage.

Why Convert to Part-Time Transfer Case?

There are several compelling reasons to consider converting a GMC transfer case from full-time to part-time operation. These include:

• Fuel Savings: As mentioned earlier, part-time four-wheel drive systems can significantly improve fuel economy, especially in urban or highway driving conditions.
• Reduced Maintenance Costs: By disengaging the front driveline when not needed, part-time transfer cases reduce wear and tear on driveline components, leading to lower maintenance costs over time.
• Improved Performance: On dry pavement, part-time four-wheel drive systems provide better handling and stability due to the absence of driveline binding.

Pros and Cons of Converting to Part-Time Transfer Case

Pros:

• Increased fuel efficiency
• Reduced wear and tear on driveline components
• Improved handling on dry pavement
• Lower maintenance costs

Cons:

• Requires manual engagement and disengagement of four-wheel drive
• May not be suitable for all driving conditions
• Can potentially increase the cost of the vehicle's transmission system

Conversion Considerations

Before converting a GMC transfer case to part-time operation, it is important to consider the following factors:

• Driving Conditions: If you frequently drive in off-road or slippery conditions, a full-time four-wheel drive system may be more suitable.
• Vehicle Usage: If you primarily use your GMC for daily commuting or highway driving, a part-time transfer case may be a better option.
• Cost: The cost of converting a transfer case from full-time to part-time will vary depending on the model year and specific transfer case type.

Conclusion

Converting a GMC transfer case from full-time to part-time operation can be a worthwhile modification for owners who want to improve fuel efficiency, reduce wear and tear on driveline components, and enhance handling on dry pavement. While there are some potential drawbacks to consider, such as the need for manual engagement and disengagement of four-wheel drive, the benefits of a part-time transfer case often outweigh the disadvantages.

Additional Resources

• GM Transfer Case Information
• Four-Wheel Drive Systems: Full-Time vs Part-Time
• Transfer Case Conversion: Part-Time to Full-Time

Tables

Table 1: Fuel Economy Comparison of Full-Time vs Part-Time Four-Wheel Drive Systems

Table 2: Common Transfer Case Shift Motor Replacement Costs

Table 3: Pros and Cons of Converting to Part-Time Transfer Case