Here's a general outline. Specific procedures may vary slightly depending on your exact model and what type of differential you have (e.g., limited-slip). Always consult your owner's manual for specifics, or a repair manual specific to your vehicle.
Tools You'll Need:
* Jack and jack stands: Essential for safely lifting the vehicle. Never work under a car supported only by a jack.
* Wheel chocks: To secure the front wheels.
* Wrench(es): The size will depend on the fill and drain plug; you'll likely need a socket wrench and possibly a box-end wrench. Check your owner's manual or a repair manual for the correct sizes. Often these are 10mm or 11mm.
* Drain pan: To catch the old gear oil.
* Funnel: To pour in the new gear oil.
* Gloves: To protect your hands.
* New gear oil: The correct type and amount are crucial. Consult your owner's manual to find the specifications (e.g., 75W-140, 75W-90). You'll need to know the capacity of your differential; again, the owner's manual will tell you.
* Torque wrench (recommended): To ensure the drain and fill plugs are tightened to the correct specification, preventing leaks.
Procedure:
1. Safety First: Park on a level surface, engage the parking brake, and chock the front wheels. Wear safety glasses.
2. Locate the Differential: The rear differential is located in the rear of the vehicle, typically between the rear wheels.
3. Locate Drain and Fill Plugs: The drain plug is usually located at the very bottom of the differential housing. The fill plug is typically located higher on the housing, often near the top. These are usually hexagonal (six-sided) or square plugs.
4. Drain the Old Oil: Position your drain pan under the drain plug. Carefully loosen and remove the drain plug, letting the old oil drain completely. This can take some time. Be careful, the oil will be hot.
5. Remove and Replace the Drain Plug: Once drained, replace and tighten the drain plug. Don't overtighten; use a torque wrench if you have one, otherwise, just snug it up.
6. Locate the Fill Plug: Find the fill plug (often a slightly smaller plug than the drain plug).
7. Add New Oil: Using a funnel, slowly add the correct type and amount of gear oil specified in your owner's manual. You'll likely need to check the oil level.
8. Check the Oil Level: The fill plug usually serves as an indicator for the level. Once oil starts to seep out, you've added enough. Replace the fill plug. Again, be careful not to overtighten.
9. Lower the Vehicle: Carefully lower the vehicle using the jack and jack stands.
10. Check for Leaks: Once the car is on the ground, inspect the area around the drain and fill plugs for any leaks.
11. Dispose of the Old Oil Properly: Take the used gear oil to a recycling center or auto parts store that accepts used oil for recycling. This is important for environmental reasons.
Important Considerations:
* Limited-Slip Differential: If your Crown Victoria has a limited-slip differential (LSD), you'll need to use the correct type of gear oil for LSDs. This is usually specified in your owner's manual.
* Torque Wrench: Using a torque wrench is strongly recommended to avoid stripping the threads on the drain and fill plugs.
This is a general guide. Consult your owner's manual or a repair manual for your specific vehicle for detailed instructions and torque specifications. If you are unsure about any part of this process, it's best to seek professional help from a qualified mechanic.
