* Parking Brake Cable/Mechanism: This is the most common cause. The parking brake cable might be sticking, partially engaged, or have a problem in the rear drum brake mechanism (if it's a drum brake system, which is likely for a 1997 Chevy work truck). Even a slight engagement can cause a wheel to lock up when reversing, as the direction of force on the brake shoes changes.
* Rear Wheel Cylinder (Drum Brakes): If you have rear drum brakes, a failing wheel cylinder could be leaking fluid internally, causing the brake shoes to remain partially applied even when the brake pedal is released. This is more likely to be a problem only when reversing because of the change in direction of force on the brake shoes.
* Brake Line Restriction/Leak: A partially blocked or leaking brake line specifically to the rear right wheel could create pressure imbalances, leading to the wheel locking up under certain conditions (like reverse).
* Differential Problem (Less Likely): While less probable, a problem within the differential could theoretically cause binding in one wheel, especially under reverse stress. This is less likely than a braking issue.
* ABS Sensor/Wiring (Even Less Likely): While your 1997 model likely doesn't have sophisticated ABS, a faulty sensor or wiring could *theoretically* cause unusual brake behavior under certain circumstances, but this is a less common cause.
Troubleshooting Steps:
1. Check the Parking Brake: Release the parking brake completely. Try reversing again. If the problem persists, the parking brake system needs further investigation.
2. Inspect the Rear Brakes: Visually inspect the rear right brake drum (if it's a drum brake system) for any obvious signs of damage, leaks, or sticking components.
3. Test for Brake Drag: With the vehicle stopped, try spinning the rear right wheel by hand. If it doesn't spin freely, you have brake drag. This strongly indicates a problem within the braking system.
4. Check Brake Fluid Level: Ensure the brake fluid level in the master cylinder is correct. Low fluid could indicate a leak somewhere in the system.
5. Check Brake Lines: Inspect the brake lines leading to the rear right wheel for any signs of damage, rust, or leaks.
Important Note: If you're not comfortable working on brakes, take your vehicle to a qualified mechanic. Brakes are critical safety components, and improper repair can lead to serious accidents. Don't drive the vehicle excessively with the problem, as continuing to use it could worsen the damage or cause an accident.
