Changing Your Front Differential, Rear Differential,
5-Speed Transmission, and Transfer Case Fluids
Application: 1998 4Runner SR5 4WD (5 speed)
Last Updated: September 27, 2006
Floor jack, jack stands, and wheel chocks
1/2" socket wrench
3/8” socket wrench
12mm socket (deep) with extension
10mm hex key or socket
12mm hex key or socket
Oil Drain Pan
5 bottles of 75W-80 Gear Lube (1 qt)
3 bottle of 80W-90 Gear Lube (1 qt)
I am providing this write up for illustrative purposes
only. Perform at your own risk. Any mods (including this one) you perform
on your vehicle is your responsibility. Commercial use of this write up
may result in legal action.
Changing your front/rear differential, 5-speed transmission, and transfer
case fluids ensures that the parts within these critical components function
with minimal wear and tear. Changing your differential and transfer case
fluids at your scheduled intervals (please refer to your manual) will help
ensure the longevity of these parts as well as your 4Runner. Refer to the
chart below for fluid type, weight and capacity information. Note: I first
used Amsoil synthetic
fluids in place of the Toyota OEM fluids which allows me to extend the change
intervals. Of course, you may use any brand of your choice. For my next
change, I am using Redline
for all my fluids. Of note, their MT-90
manual transmission fluid is the best. In fact, the Amsoil 75W-90 was
too slippery for the transmission. Based on my personal experience, I do
not advise putting it into your manual transmission.
Type & Weight
Oil API GL-4 or GL-5
Qt (36 oz)
Gear Oil API GL-5
Qt (33 oz)
Gear Oil API GL-5
Qt (69 oz)
Gear Oil API GL-5
Qt (78 oz)
For my fluid
changes, I started with the rear differential, moved onto the transfer
case, then the manual transmission, and finally finished off with the
front differential. Note: it's a good idea to do both your oil change
and the front differential at the same time as you will need to pull off
the front skid plate anyways. You may do it in any order you wish.
Changing Your Rear Differential Fluid
by lowering your spare tire and moving it out of the way. Now chock your
rear wheels and jack up your 4runner and set your jack stands in place.
Fortunately, I can work semi-comfortably in this area without jacking
it up in the rear thanks to a mild PP 1” lift. Unbolt the 12mm rear
brake cable bolt. This will allow you to maneuver your 24mm socket on
the ½ inch socket wrench onto the top 24mm (fill) bolt. Turn it
counterclockwise to remove the plug. After removing this plug, remove
the bottom 24mm drain plug. Allow it to drain out.
Note: one reader provided me feedback that the 24mm drain bolt is soft
metal. He used a 12 point instead of 6 point socket and rounded it off.
Thus as a precaution, use a 6 point socket and use some PB Blaster the
night before to loosen the plug.
the tire by cranking counter-clockwise
12mm bolt (P) to allow room for your 24mm socket; remove fill bolt
(F) first and then drain bolt (D)
probably notice some metal shavings on the bottom (drain) bolt. Clean
the shavings off. After the fluid has completely drained, re-fasten the
bottom drain bolt with a “crush” washer/gasket.
off the magnetic drain plug
hand pump into your bottle of Amsoil and insert the other end into the
fill hole. Pump approximately 2.6 quarts (78 oz) of the gear fluid in.
When the fluid just begins to seep out of the fill hole, re-fasten the
the barbed end into the fill hole
2.6 qts of gear lube in
the rear brake cable bolt and move onto the transfer case.
Changing Your Transfer Case Fluid
This one is the easiest of the three. Using the same 24mm socket,
remove the top “fill” bolt and set aside. Next, move your
drain pan about 8 to 12 inches towards the rear of bottom drain plug.
Now unbolt the drain bolt. Careful because the transfer fluid will shoot
out like water from a busted dike from an old 1930’s movie (don’t
ask me how I know this).
ALWAYS remove the fill hole first!
that fluid will shoot out like a missile
the fluid to drain, attach washers to both bolts and re-fasten the bottom
“drain” bolt. Pump in 1.1 Quarts (33 ounces) of gear lube
into the transfer case. When the fluid just begins to seep out of the
fill hole, re-fasten the fill bolt. You’re done and now onto the
Your Manual Transmission Fluid
Thank goodness for manual transmissions: its a very simple drain
and fill! As always, unbolt the fill plug first. It is located on the
driver's side. It's easier to use a crescent wrench here to remove the
24mm bolt. Next, place your oil pan underneath the drain plug and then
remove the bolt, located on the passenger side, with a 24mm socket. Place
both bolts/washers in a safe location and let the transmission fluid drain.
the 24mm drain plug/washer. This one is very easy to remove.
the 24mm fill plug w/ a crescent wrench. Space is a little tight here,
but its doable.
transmission fluid comes to a slow drip, re-fasten the drain plug. Next,
fill the transmission with 2.3 quarts (69 oz) of Amsoil 75W-90 Gear Lube.
Replace the fill plug and then you're ready to move onto the front differential.
Changing Your Front Differential Fluid
This one requires one tedious step: removing the front skid plate.
You’ll definitely need to jack up your 4Runner for this one, so
go to it. To remove the skid plate, see the graphic below. There are a
total of six 12mm bolts that need to be removed. Begin by removing the
front three bolts. Then remove the back two bolts. Finally, remove the
middle bolts. You will notice that in the front of the skid plate, it
will “hang” because of the three “clips”. Pull
off the skid plate by pulling upwards and towards the front. Set aside
and keep the bolts in a safe place.
the six 12mm bolts
the fill and drain is identical in procedure to the transfer case. The
fill plug uses a 10mm hex and the drain plug is a 12mm hex.
the front differential drain plug w/ a 10mm hex. Excuse the blurry
the front differential drain plug w/ a 12mm hex. Some 3rd gen owners
(99 to 02) have written to me and said that their front diff drain
and fill plugs are both 12mm. Have both just in case.
the drain plug w/ a new crush washer/gasket. Fill your front differential
oil w/ the hand pump with 1.2 quarts of gear fluid.
down there, consider changing your oil. Removing the oil filter is MUCH
easier with the skid plate off. Here’s my write up on how
to change your oil.
the skid plate in reverse order. Now, take your 4Runner for a short drive
in both 4Hi and 4lo to re-lubricate all assemblies.
and Learning Points
- When removing the fill plug on the manual transmission housing, space
is a little tight. However, you can use a normal crescent wrench to do
- I had the most difficult time removing the drain plugs on the front
and rear differential. Try to clean out as much gunk as possible with
a good engine cleaner and a toothbrush. Also consider using PB blaster
to loosen up the plugs.
the skid plate is easily accomplished if you have an extra jack stand
on hand to hold one end up (the back end, for example) while unbolting
- I received
a PM from MTL_4runner who confirmed with a dealership that for 3rd gens from 1996-1998, the
front diff plugs use a 10mm and 12mm for the drain and fill plugs, respectively.
For 1999-2002, the drain and fill plugs are both 10mm. Thanks, MTL!
or feedback? Email me and I'll try to get back to you. If this article
helped you save time, money or just made things more convenient for
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