The gear oil in your rig keeps friction to a minimum and ensures the long life of your differential gears. Changing the oil in the rear differential is an easy maintenance activity that keeps your off-road rig motoring forward, saves money and allows you to learn a little more about your 4×4 adventure vehicle (you never know when that knowledge will come in handy on the trail).
The first big decision is what oil to use. The Toyota maintenance manual for a 2007 FJ Cruiser specifies: Hypoid gear oil APL GL-5. We went with Amsoil Severe Gear SAE 75W-90 synthetic extreme pressure lubricant, formulated for sever duty applications. If you are curious why we picked Amsoil, read this gear oil comparison. Our FJ Cruiser is equipped with an e-locker which means it requires between 3.01 and 3.12 quarts to properly fill the rear axle housing.
The other item to pick up before you get started are new drain and fill plug gaskets (part# 1215710010). Unless your on the trail working a field repair, don’t try save $2.00 by reusing these little items.
Most back yard mechanics will have the tools required to perform this simple activity. The tools you will need include:
- 24mm socket and socket wrench
- torque wrench
- funnel with flexible tube (Hopkins FloTool 10704 Spill Saver Measu-Funnel)
- shop rags
- oil catch pan (Blitz 11837 10 Quart Oil Drain)
- nitrile or latex gloves (this is a messy job)
Ok enough shop talk and prep…
Put the rig on a flat level spot to ensure good draining and proper refill. Tip: clean the axle housing with soapy water and a scrub brush to remove the road and trail gunk. This will prevent any dirt from falling in to the differential while changing the oil.
Using a 24mm socket remove the fill plug located in the middle(ish) of the rear axle housing. By removing the fill plug first the housing will be able to breath allowing the differential oil to drain more quickly.
With the oil catch pan in place remove the drain plug, located on the bottom of the rear axle housing, using a 24mm socket. If your going to use gloves, this is the time to wear them.
The drain plug has a magnetic insert designed to attract and hold tiny metal shavings that become suspended in the oil. Yes these are little bits of your gears. Inspect the drain plug checking for any chunks and observe how much has accumulated. This will give you an idea of what has been going on inside your differential.
Even with the fill plug removed, it will take a while for the oil to completely drain, which is good since it will give you time to grab the shop rags and clean the plugs, removing all the gunk and accumulated metal shavings. When your done the plugs should be clean and dry. Don’t forget which is which.
Once the oil is fully drained, wipe the area clean and re-insert the drain plug (Be sure to use the correct plug) with a new gasket and hand tighten. Set the torque correctly on your torque wrench and tighten down the drain plug. The Toyota maintenance manual states the torque specifications for both the drain and fill plugs as 36 foot pounds for our 2007 Toyota FJ Cruiser.
Remember that funnel with flexible tube? Getting the oil out of the bottle and into the axle housing through that little hole can be tricky. One of the advantages of the Hopkins FloTool 10704 Spill Saver Measu-Funnel is that the flexible tube funnel cap will screw directly on to the Amsoil quart bottles. The cap has an open and close position preventing spills as you position the bottle and hose into place.
Squeezing out three plus quarts of thick 90 weight through the tube and into the axle housing will take awhile so get comfortable. It works best if you give the quart bottle a few long squeezes and than allow air to flow back into the bottle followed by a few more good squeezes.
Checking the fill level on flat ground is easy. The oil should barely begin to run out or just about to run out (within 5mm of the fill opening).
Hand tighten the fill plug and new gasket followed by torquing down the plug to Toyota specifications (36 ft.*lbf for the 2007 FJ Cruiser).
Give everything one more wipe down and check for leaks followed by a drive around the block. Double check for drips and leaks when the test drive is complete.
There comes a time in every rig’s life when it’s gear oil needs a change to keep all the gears turning smoothly. Changing the rear differential oil on a Toyota FJ Cruiser is a simple maintenance job anyone can do with a little know how and about 60 minutes.
Be sure to change the gear oil in the transfer case as well. Learn how with our step by step transfer case oil change video.