How to Change a Differential Cover and Gasket on a Car
The differential cover is also referred to as the rear end cover. The most common reason to replace it is because it's leaking.
The gasket that is between the rear end and the cover can break down and crack which can cause leaking over a period of time. Anytime you remove the cover, you need to install a new gasket.
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Things You'll Need
- Sockets and extensions to to fit the bolts holding the cover in place.
- Torque wrench
- Large flat-head screwdriver
- Safety glasses
- Rubber gloves
- Paint scraper or sturdy putty knife
- Single-edge razor blade
- Degreaser
- Floor jack
- Jack stands
- Wheel chocks
- Catch basin
- Penetrating lubricant
- Lubricant/cleaner for the threaded bolts
- Flood light and flashlight
- Small hammer
- Small funnel
- New differential gasket per specs for your car
- Differential fluid per specs for your car
- Rags and hand cleaner
Instructions
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Disconnect your negative battery terminal before starting this job. Set the emergency brake. Set your wheel chocks in front of the front tires. Jack up the car and place jack stands under the frame or rear axle. The car should be high enough so you can access the rear end cover comfortably and safely.
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Don rubber gloves and eye goggles. Goggles should always be worn when under the car. Set up your lighting under the car.
Place some cardboard under the rear end cover and spray the cover from all sides with degreaser. Remove grease and sludge so it will be easier to see what you are doing and give you a clean work environment.
Pull out the cardboard with all the mess on it. -
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Have your flashlight ready in case you need it. Place the catch basin under the rear end.
Remove the drain plug, if applicable, and allow the fluid to drain. Otherwise, remove the bolts on the rear end cover. Typically there are eight or more bolts depending on your particular car. If you have a problem loosening any, spray with the penetrating lube. Keep track of all the bolts you remove. -
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Once all the bolts are removed you should be able to pull the cover straight off. You may have to wedge the flat-head screwdriver in and give it a little twist or place the putty knife or scraper between the mating surfaces and pry just a bit. If it is still stuck, you can gently tap the end of the scraper with your hammer. You don't want to knick, bend or distort the metal in the process.
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Once you've removed the cover, bring it over to your work bench and with your scraper and razor blade, thoroughly clean any remaining gasket material or debris from the mating surface. If you are replacing the cover, your new one should already be clean, but in any case you also need to clean the mating surface on the rear end under the car. Both mating surfaces should be completely free of any debris and very smooth or you may have a leak later on.
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Test the fit of your new gasket by lining it up with the bolt holes to be sure you have the correct one. Apply your gasket sealer to the mating surface of the cover -- make sure the sealer is on the entire mating surface, about 1/8-inch thick, and then place the gasket on the cover, making sure that the bolt holes line up exactly with the pre-cut holes in the gasket. Apply gasket sealer on the rear end mating surface as well, or the top side of the gasket. Let the sealer set for a few minutes.
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Apply thread cleaner/lube on the bolts you removed from the cover. They should be clean and free of any debris or grit. Set them under the car and get your torque wrench set up for the proper torque and place it under the car in your work area.
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Line the cover up with the openings for the bolts on the rear end and hand tighten the bolts in as far as you can.
Using your torque wrench, start tightening the bolts in a star pattern. The general torque for a plastic rear end cover is usually 10 to 15 foot-pounds and for metal, 25 to 35 ft lbs. Check your vehicle's torque setting through a mechanic or service department at a dealership. It is very important that all bolts be evenly tightened with the use of the torque wrench. The above torque settings are general examples only. -
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There is a filler plug on the top portion of the rear end itself or the cover. You may have to feel around and use your flashlight to find it.
Remove the filler plug and add new fluid, using your funnel, until it is full to the top of the filler hole. A way to test if it is full or not, since there is no dipstick to pull out and check, is to stick a finger into the opening, if it is full, your finger will come out wet showing you the level, which needs to be near the top. Sometimes a standard funnel will not give you the proper filling angle you need and you may have to devise a cardboard or heavy paper funnel yourself. -
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Before putting the filler plug back into the rear end, take a good look at it and make sure the threads are clean and without any grit. Install the plug tightly. No special torque specs here.
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Remove your tools from under the car. Lower the car to ground, release your emergency brake and remove the wheel blocks. Start up the car and with your foot firmly on the brake, change into all gears slowly once or twice. Now with the car back into Park, check below to see if there are any leaks coming from the gasket area.
If it looks good and dry then test drive a short distance and then come back and check again for leaks.
If it is leaking it would usually mean that the rear end bolts are not tight enough or torqued evenly, the filler plug is not tight enough or possibly started in crooked, or the gasket is not in the proper position.
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Tips & Warnings
Routine maintenance is to check the level of differential fluid every 15,000 miles.
Be sure the car is secure on proper jack stands before going under it.
Dispose of the old fluid responsibly.
Always wear safety glasses while under the car.
