Here's a general outline of the process. Specific steps may vary slightly depending on your axle configuration (e.g., single or dual rear wheels). Always consult a repair manual specific to your truck's year, model, and axle type for detailed instructions and torque specifications. A factory service manual is your best resource.
Tools and Materials You'll Need:
* Repair Manual: Absolutely essential!
* Jack and Jack Stands: Securely support the truck.
* Wheel Chocks: For safety.
* Lug Wrench: To remove the wheels.
* Torque Wrench: Crucial for proper tightening.
* Socket Set and Wrenches: Various sizes.
* Pry Bar or Punch: To help remove the axle shaft.
* Hammer: (Possibly a rubber mallet)
* New Axle Seal: Get the correct seal for your axle.
* New Axle Seal Installer: This tool helps avoid damaging the new seal.
* Brake Cleaner: To clean the axle housing.
* Penetrating Oil (PB Blaster, etc.): To loosen bolts.
* Grease: For the new seal and axle.
* Safety Glasses and Gloves: Protect yourself.
* Drain Pan: For any fluid that might spill.
General Steps (Consult your repair manual for specifics):
1. Safety First: Park on a level surface, engage the parking brake, and use wheel chocks.
2. Raise and Support the Truck: Safely lift the rear of the truck and secure it on jack stands.
3. Remove the Wheel(s): Remove the lug nuts and take off the wheel(s).
4. Remove the Brake Caliper and Rotor (Possibly): Depending on your setup, you may need to remove the brake caliper and rotor to access the axle seal. Support the caliper with a wire or hook to avoid stressing the brake line.
5. Drain the Differential: Completely drain the differential fluid into a drain pan.
6. Remove the Axle Shaft (Possibly): This is often the most challenging part. You may need to disconnect the driveshaft and remove the axle shaft from the differential. This will require removing various bolts and may involve using a pry bar or punch (carefully!).
7. Clean the Axle Housing: Thoroughly clean the axle housing bore where the seal sits, removing any old seal remnants, dirt, or debris. Use brake cleaner.
8. Install the New Axle Seal: Use the seal installer tool to carefully install the new seal, avoiding any damage. Apply a light coat of grease to the seal lip.
9. Reinstall the Axle Shaft (If Removed): Carefully reinstall the axle shaft, ensuring it's seated properly.
10. Reinstall Brake Components (If Removed): Reinstall the rotor and brake caliper.
11. Reinstall the Wheel(s): Tighten the lug nuts to the proper torque specification.
12. Refill the Differential: Add the correct type and amount of differential fluid. Refer to your owner's manual or repair manual for specifications.
13. Lower the Truck: Carefully lower the truck from the jack stands.
14. Torque Check: Check all bolts and lug nuts for proper torque.
Important Considerations:
* Axle Type: The process will differ slightly based on whether you have a 14-bolt, 10-bolt, or other axle type.
* Dual Rear Wheels: Dual rear wheels add complexity.
* Torque Specifications: Use a torque wrench and adhere to the manufacturer's specified torque values for all bolts. Incorrect torque can lead to leaks or component failure.
* Differential Fluid: Use the correct type and amount of differential fluid recommended for your truck.
Again, this is a general outline. You must consult a repair manual specific to your 2003 GMC 2500HD Sierra to ensure you have the correct steps and torque specifications. This is a complex repair with the potential for significant damage if done incorrectly. If you're unsure about any step, seek professional help.
