Tools You'll Need:
* Jack and jack stands
* Lug wrench
* Wheel chocks
* Socket set (metric)
* Wrench set (metric)
* Hammer
* Screwdrivers (flathead and Phillips)
* C-clamp or brake spring compressor tool (essential!)
* Wire brush
* Brake cleaner
* Drum brake grease
* New brake shoes
* New wheel cylinders (recommended, even if they seem fine)
* New hardware (springs, clips, etc.) – replace all old hardware
* Possibly a new brake drum (if scored or damaged beyond repair)
Repair Procedure:
1. Safety First: Park on a level surface, engage the parking brake, chock the wheels, and securely lift the vehicle using the jack. Place jack stands under the frame near the axle. Never work under a vehicle supported only by a jack.
2. Remove the Wheel: Loosen the lug nuts before lifting the vehicle. Remove the wheel and set it aside.
3. Inspect the Drum: Note the condition of the drum. If it's severely scored or damaged, it'll likely need replacement. If it's just rusty, you can try cleaning it.
4. Remove the Drum: Sometimes the drum can be removed by hand after carefully tapping it with a rubber mallet. If it's stuck, you may need to use a drum puller or gently tap the drum around its circumference while applying leverage with a pry bar (carefully!).
5. Inspect the Brake Components: Examine the brake shoes, wheel cylinders, springs, and other components for wear, damage, or leaks. Replace anything that looks worn, damaged, or questionable. Leaking wheel cylinders are a common cause of brake failure.
6. Remove the Brake Shoes: Carefully remove the brake shoes using the proper technique. This involves compressing the brake springs using a C-clamp or a specialized brake spring compressor tool. This is the most difficult and potentially dangerous part of the job. Take your time and be careful not to damage the springs or break them. A broken spring can cause injury. There are many videos online demonstrating this step; viewing a few before you start is recommended.
7. Remove the Wheel Cylinders: Once the shoes are off, carefully remove the wheel cylinders. Replace them with new ones, even if they seem okay. Old wheel cylinders can leak, leading to brake failure. Carefully note the orientation of the cylinders before removing them to ensure correct reinstallation.
8. Clean Everything: Thoroughly clean all components with brake cleaner.
9. Install New Components: Install the new brake shoes, wheel cylinders, springs, and hardware. Refer to your repair manual for the correct orientation and installation procedures. This involves carefully repositioning the springs and adjusting the brake shoe self-adjusters.
10. Adjust the Brake Shoes: After everything is installed, carefully adjust the brake shoes to ensure proper clearance between the shoes and the drum. This step is critical for proper braking.
11. Install the Drum: Carefully install the drum, ensuring it seats properly. It should slip on easily.
12. Reassemble Everything: Reinstall the wheel and tighten the lug nuts to the proper torque specification (consult your repair manual). Lower the vehicle.
13. Test the Brakes: Test the brakes carefully in a safe area, away from traffic. The brakes should engage smoothly and firmly. If not, you may need to re-adjust them or address other issues.
Important Considerations:
* Brake fluid: If you replace the wheel cylinders, you'll likely need to bleed the brakes to remove air bubbles from the brake lines. This process requires a helper and a brake bleeder kit.
* Repair manual: A repair manual specific to your 1994 GMC Sierra is strongly recommended. It will provide detailed instructions, diagrams, torque specifications, and other important information.
* Professional help: If you're not comfortable performing this repair yourself, take your vehicle to a qualified mechanic. Brake failure can be dangerous, and improper repair can lead to serious consequences.
This is a complex repair. If you're unsure about any step, don't attempt it. Safety should always be your top priority.
