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Front/Rear Differential Fluid Replacement

While I replaced the transfer case fluid on my 2003 Toyota 4Runner, I decided to replace the front and rear differential fluid at the same time. The differential fluid lubricates the internal gears, which help transfer power from the driveshaft to the axle. If I want my car to continue running smoothly, I needed to get this maintenance item done. I followed an excellent write-up posted by snowbizx on T4R.org here, which includes both the process for replacing the transfer case fluid and front and rear differential fluids.

First jacked up the car and made sure it was chalked and level.

4th gen 4runner differential fluid and transfer case fluid - raising and support vehicle

Parts Needed for Front and Rear Differential Fluid Replacement

The original specifications for the 4th Gen 4Runner calls for the following: SAE 75W-90, Hypoid Gear Oil API GL-5. I went with the commonly used and readily available, Mobil 1 Synthetic Gear Lubricant LS 75W-90.

4th gen 4runner differential fluid and transfer case fluid - plews fluid quart pump

This fluid quart pump makes the job easy since you have to move the fluid from the bottle up into the differential fill hole. You can purchase this through Amazon through the link below:
Plews 55001 Lubrimatic Fluid Quart Pump, Fits Standard Quart Bottles

4th gen 4runner differential fluid and transfer case fluid - mobile1 synthetic gear lubricant 75w-90

These bottles can be bought through the link below:
Mobil 1 104361 75W-90 Synthetic Gear Lube – 1 Quart

According to the owner’s manual, a Hypoid gear oil API GL-5 with viscosity of 75W-90 (front) and 80W or 80W-90 (rear) should be used. It also states the 1GR-FE V6 engine has a differential oil capacity of:

  • 2WD models: 3.2 qt
  • 4WD models: 1.6 qt (front), 3.2 qt (rear)
4th gen 4runner differential fluid and transfer case fluid - various gaskets

Ignore the part number above, the Toyota dealership parts department put all of my plug gaskets into one bag. I usually recommend getting your parts at the local dealership unless you can find a good deal online that doesn’t try to gouge you on shipping costs. Part numbers for what you might need are listed the link to the forum thread at the top of this page.

Rear Differential Fluid Replacement

4th gen 4runner rear differential location

You see here the rear differential with the fill plug up top and the drain plug at the bottom.

4th gen 4runner - draining rear differential

Remember to remove the fill plug first before removing the drain plug. First, it helps with air flow in draining the fluid. More importantly, you want to make sure that you don’t drain the fluid, then find out you can’t remove the fill plug, and then get stuck with a differential with no fluid.

4th gen 4runner rear differential plug with goop

Yucky gunk at the bottom of the drain plug.

4th gen 4runner - filling rear differential with gear oil

Using the pump that goes directly on the quart bottles, it’s pretty easy to pump the fluid up into the rear differential.

4th gen 4runner rear differential fluid replacement complete

After refilling, reinstall and torque the fill plug.

Front Differential Fluid Replacement

4th gen 4runner - draining transfer case

Do the same process for the front differential. Again, fill plug up top and drain plug near the bottom.

Refilling the front differential fluid…

4runner 4th transfer case fluid replaced

And now re-tighten everything back up again and we are completely done.


Hi there! I'm Scott and I run The Track Ahead. My goal is to provide helpful articles and tutorials based on my experience and research related to car maintenance and automotive detailing. When I'm not writing and not working my day job, you can find me spending time with my family and working on home and car projects.

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