1. Preparation:
* Safety First: Disconnect the battery's negative terminal. Support the transmission properly – either with a transmission jack or securely using jack stands. Wear safety glasses and gloves.
* Gather Tools: You'll likely need a variety of tools, including screwdrivers (possibly a large flathead), pliers (possibly needle-nose), a small pick or punch, a clean rag, brake cleaner, and possibly a seal installer (to avoid damaging the new O-ring).
* Drain Transmission Fluid: Completely drain the transmission fluid before you begin. This will make the job cleaner and safer.
2. Accessing the O-ring:
* Identify the Seal Location: Locate the exact point where the driveshaft connects to the transmission. The O-ring is usually seated in a groove on the transmission output shaft or the driveshaft flange.
* Remove the Driveshaft: You'll almost certainly need to disconnect the driveshaft from the transmission. This usually involves unbolting the driveshaft flange from the transmission.
* Inspect the Seal: Once the driveshaft is removed, carefully inspect the O-ring. If it's brittle or damaged, it needs replacing. Note its size and shape for ordering a replacement.
3. Removing the Old O-ring:
* Gentle Persuasion: Try to gently pry the old O-ring out of its groove using a small flathead screwdriver or a pick. Work your way around the circumference of the O-ring, carefully avoiding scratching the mating surfaces. A little brake cleaner can help loosen the old seal.
* Avoid Damage: Be extremely careful not to gouge or damage the transmission housing or the output shaft. Any damage here could lead to leaks.
* Stubborn O-rings: If the O-ring is stuck, a very thin, flat tool might help. Heat (carefully applied with a heat gun on low setting) can sometimes help soften the rubber, but be cautious not to overheat the transmission housing.
4. Installing the New O-ring:
* Clean Thoroughly: Clean the groove where the O-ring seats using brake cleaner and a rag. Make sure all debris and old sealant are removed.
* Lubricate: Lightly lubricate the new O-ring with transmission fluid (the type specified for your transmission). This will help it seat properly.
* Installation: Carefully install the new O-ring into its groove. A seal installer tool is highly recommended to avoid damaging the O-ring. Work the O-ring evenly around the groove.
* Reassemble: Carefully reinstall the driveshaft, ensuring it is properly aligned and bolted tight (to the manufacturer's specified torque).
5. Final Steps:
* Refill Transmission Fluid: Refill the transmission with the correct type and amount of fluid (consult your repair manual).
* Test Drive: Test drive the vehicle carefully to check for leaks.
Important Considerations:
* Repair Manual: A repair manual specific to your 1983 Chevy G20 van and its transmission is essential. It will provide diagrams, torque specifications, and specific procedures.
* Transmission Type: The exact procedure will vary slightly depending on the type of transmission in your van (e.g., TH350, TH400, etc.).
* Professional Help: If you are not comfortable performing this repair yourself, it's best to take your van to a qualified mechanic. Improper repair can lead to significant transmission damage.
This information is for guidance only. Always prioritize safety and consult a reliable repair manual before attempting this repair.
