However, if you're determined to do it yourself, here's a general outline. This is not a complete, step-by-step guide, and specific procedures may vary depending on your Blazer's transmission type (automatic or manual) and engine. Always consult a repair manual specific to your vehicle's year, make, model, and engine for detailed instructions and torque specifications.
Tools You'll Likely Need:
* Repair Manual: Absolutely essential.
* Jack and Jack Stands: Safety first!
* Wheel Chocks: For added safety.
* Transmission Jack: Highly recommended for supporting the transmission.
* Drain Pan: For transmission fluid.
* Sockets and Wrenches: Various sizes, including metric and standard.
* Torque Wrench: Crucial for tightening bolts to the correct specification.
* Pry Bar: May be needed to carefully separate components.
* New Transmission Seal: Make sure you get the correct one for your vehicle.
* Transmission Fluid: The correct type and amount for your transmission.
* Shop Rags or Paper Towels: For cleaning.
* Gloves: To protect your hands.
* Safety Glasses: To protect your eyes.
General Steps (Highly Simplified):
1. Safety First: Disconnect the negative battery terminal. Secure the vehicle on jack stands after raising it safely. Chock the wheels.
2. Fluid Removal: Drain the transmission fluid completely.
3. Access the Transmission: This will involve removing various components, likely including the driveshaft, possibly the exhaust system (at least partially), and possibly some other components depending on the seal's location. Your repair manual will detail exactly what needs to be removed.
4. Support the Transmission: Use the transmission jack to support the transmission as you disconnect components.
5. Remove the Old Seal: Carefully remove the old seal, taking care not to damage the transmission housing. A small pry bar might be helpful, but use caution.
6. Clean the Surface: Thoroughly clean the transmission housing where the new seal will be installed. Any debris can prevent a proper seal.
7. Install the New Seal: Carefully install the new seal, making sure it's seated correctly. A seal installer tool may be helpful.
8. Reassembly: Reassemble all components in reverse order of removal, carefully tightening bolts to the correct torque specifications using your torque wrench.
9. Refill Transmission: Refill the transmission with the correct type and amount of transmission fluid. Consult your repair manual.
10. Check for Leaks: Carefully inspect for any leaks around the new seal.
11. Test Drive: After letting the transmission settle, take it for a test drive to make sure everything is working correctly.
Important Considerations:
* Transmission Type: The process differs significantly between automatic and manual transmissions.
* Seal Location: There are multiple seals on a transmission; you need to know *which* seal you're replacing.
* Torque Specifications: Incorrect torque can damage the transmission. Use a torque wrench and consult your repair manual.
* Fluid Type: Using the wrong transmission fluid can severely damage your transmission.
Again, I strongly recommend consulting a repair manual specific to your 1999 Chevy Blazer before attempting this repair. This is a complex job with the potential for serious damage if not done correctly. If you're not comfortable with this level of mechanical work, take your Blazer to a qualified mechanic. The cost of a professional repair is significantly less than the cost of a damaged transmission.
