I. Preparation is Key:
1. Gather Tools and Materials: You'll need a complete set of metric and standard sockets and wrenches, a torque wrench, a transmission jack, engine hoist (highly recommended), a rear main seal installer and remover tool (essential to avoid damage), a new rear main seal (ensure it's the correct one for your engine), gasket sealant (appropriate for oil seals), rags, clean engine degreaser, and safety glasses.
2. Safety First: Disconnect the negative battery terminal. Work in a well-ventilated area. Use jack stands to securely support the vehicle. Wear appropriate safety gear.
3. Drain Fluids: Drain the engine oil and transmission fluid completely. Allow ample time for the fluids to drain.
II. Transmission Removal (Most Common Method):
1. Disconnect Components: Disconnect the driveshaft, shift linkage, speedometer cable, and any other components connected to the transmission.
2. Support the Transmission: Use a transmission jack to securely support the transmission.
3. Remove Transmission: Carefully separate the transmission from the engine. This is usually done by removing the bellhousing bolts. This step requires significant effort and potentially specialized tools.
III. Rear Main Seal Replacement:
1. Access the Seal: With the transmission removed, you'll have access to the rear main seal. It's located at the rear of the engine block, where the crankshaft exits.
2. Remove the Old Seal: Use a rear main seal remover tool to carefully remove the old seal without damaging the crankshaft. Be cautious not to scratch the crankshaft journal.
3. Clean the Surfaces: Thoroughly clean the crankshaft journal and the seal housing in the engine block. Use a degreaser and clean rags. Remove any debris or old sealant.
4. Install the New Seal: Use a rear main seal installer tool to carefully install the new seal. Make sure it's seated correctly and evenly. Avoid forcing it.
5. Inspect for Damage: Inspect the crankshaft for any scoring or damage. If damage is present, it might require crankshaft repair or replacement.
IV. Reassembly:
1. Install Transmission: Carefully reinstall the transmission, ensuring all bolts are tightened to the correct torque specifications (consult your repair manual).
2. Reconnect Components: Reconnect all previously disconnected components.
3. Refill Fluids: Refill the engine oil and transmission fluid to the correct levels.
4. Check for Leaks: Start the engine and check for any leaks around the rear main seal. Let the engine run for a while to allow the oil to circulate and settle. Check the oil level again.
V. Important Considerations:
* Repair Manual: This is crucial. A factory service manual specific to your 1986 Dodge 318 will provide detailed diagrams, torque specifications, and step-by-step instructions.
* Two-Piece Seal vs. One-Piece Seal: The 1986 318 might use a one-piece or two-piece rear main seal. Ensure you have the correct replacement for your engine.
* Professional Help: If you're not comfortable with this repair, it's best to take your vehicle to a qualified mechanic. This job can be very challenging, and incorrect installation can cause significant damage to your engine.
This is a simplified overview. Attempting this repair without proper experience and the right tools can lead to significant damage to your engine. Always consult a reputable repair manual and consider seeking professional help if you lack the necessary experience.
