If you prefer to do your own maintenance, don’t forget about the rear differential. Changing the fluid is easy, according to ChrisFix. It’s something that you should do pursuant to your vehicle manufacturer’s recommendations as metal builds up in the differential – and gear oil breaks down after a while.
What do I need to change the gear oil in my vehicle?
You’ll need gear oil and a gasket or RTV if you can’t find a gasket. Use a brand of RTV that is made for rear differentials, such as Permatex red RTV. You’ll also need limited slip additive if your rear is a limited slip rear.
You’ll also need:
- Plastic scraper
- Screwdriver
- Ratchet and sockets
- Oil drain pan
- Brake clean
To learn more about the steps for changing the gear oil in your vehicle’s rear differential, keep reading for the steps and some tips.
Get Everything Ready
Before changing the rear differential fluid, take the drain plug out first. If you can’t get the drain plug out or it strips, you won’t be able to do the job since you won’t have a way to fill the differential up as long as the plug won’t come out.
The drain plug is magnetic. Once you get it out, clean off the metal shavings stuck to it. Reinstall the drain plug to prevent the differential from getting contaminated. You don’t have to tighten it down – hand-tight is good enough, since you’ll be removing it again.
Slide the oil catch pan under the differential. Make sure it’s under the cover. Gear oil is sticky, and if you make a mess, it’ll be difficult to clean up.
Starting to the left of the top differential cover bolt, remove the bolts until you get to the second bolt before the bottom bolt. Remove the same bolts on the other side, leaving the top bolt and three bottom bolts in place.
Remove the three bottom bolts. Loosen the top bolt and unscrew it about halfway. Using the screwdriver, carefully pry the bottom of the cover off the rear differential. Let the gear oil drain.
If you take all of the bolts out, when you take the last bolt out, the cover will land in the oil catch pan with a splash. Not only will you be irritated at having to clean up a big mess, but the stinky gear oil will splash, making you stinky.
Once the oil drains, carefully remove the top bolt while holding the cover.
Clean the Cover and the Surface of the Differential
Peel the gasket or RTV off the cover and the surface of the differential. Use brake clean to make it easier. If you have to scrape any hard bits of gasket or gasket maker off, use a plastic scraper. A metal scraper could gouge the surfaces, causing them to leak.
Clean the inside of the cover with brake clean. Get most of the oil and all the metal shavings out. Spray some brake clean on a towel to clean off the mating surface on the differential. Do not get any brake clean inside the differential.
Some rear ends have magnets inside the cover. If yours does, remove the magnet and clean it off with brake clean, making sure to get all of the metal shavings off the magnet.
Check the mating surface for scratches and divots. If there are any, you’ll have leaks. This is less of a problem if you are using RTV to make the gasket, since the RTV will fill in small scratches and divots.
Install the Gasket and Reinstall the Cover
If you are using a gasket when changing the gear oil, make sure it lines up with all the holes on the cover. To keep it in place while installing the cover, you can do one of two things:
- Insert the top and bottom bolts through the holes in the cover and the gasket.
- Smear a thin coat of RTV on the cover. Let it set until it gets tacky. Line the gasket up with the holes; then press it into the RTV. The RTV will hold the gasket in place.
If you are using RTV to make a gasket, put a 1/4-inch thick bead of RTV around the inside of the bolt holes on the cover. Keep a continuous bead going all the way around the cover. Let the RTV set for about 15 minutes or until it gets tacky.
Insert a cover bolt through the top and bottom cover holes. Carefully line the cover up on the rear differential. Starting with the bottom bolt, turn it in until you feel resistance, then repeat with the top bolt.
Insert the rest of the bolts and hand-tighten them until you feel resistance. When tightening the bolts, tighten them in a star pattern. Using the ratchet and socket, tighten the bolts in a start pattern until you see RTV squeezing out between the cover and the rear differential mating surface.
Let the RTV cure for an hour. Set a torque wrench to 10 foot-pounds of torque. Tighten the bolts in a star pattern to 10 foot-pounds. Set the torque wrench to the manufacturer’s recommended torque for your vehicle – usually 25 to 35 lb-ft.
Tighten the bolts in a star pattern to the recommended torque.
Remove the fill plug. Put the pump hose into the gear oil and the other end into the fill hole. Pump the gear fluid into the rear differential until you see it start leaking out of the fill hole. Remove the pump hose.
Stick your finger into the fill hole. It should have gear oil on it when you pull it out. Torque the fill hole plug to 15 lb-ft.
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