Authors: Erik Bibelheimer, Joe
Micciche, November, 2003
The axleshaft and backing plate: I had some
cleaning up to do.
When a rear axle seal goes bad, it's typically noticeable by gear oil leaking all over a rear wheel, and it may get into the brake drum and reduce rear brake feel.
Common causes of axle seal failure are plugged differential breathers or worn wheel bearings. Less common causes can be a bent axle housing or shaft.
When the stock breather is unable to vent the diff, the internal pressure will find relief somewhere in the system: usually at the axle seal. So, if you have a leaking seal, be sure to check the breather for proper
better yet, replace it with an extended breather.
Axle Shaft Removal and Inner Seal Replacement
The brake assembly and axle/backing plate
prior to removal.
The e-brake cable is off, and the hydraulic
line is "gravity bleeding".
To replace a rear axle seal or bearing, the rear axle should be placed securely on jackstands, and the tire removed. Place a drain pan under the end of the tube to catch any gear oil which may drip. Once the tire is off the vehicle, remove the retaining pin from the emergency brake lever mechanism at the backing plate and move the cable out of the way.
1990 and later 4runners will need to remove the brake drum, unhook the brake cable from the lever inside, unbolt the cable sleeve from the backing plate, and slide the cable out. Then, the hydraulic brake line can be removed from the backing plate. If you don't have a flare tool, remember the line fitting nut is soft and subject to rounding off, so be cautious. The brake lines will "gravity bleed" while disconnected, so you may want to find a way to plug them to keep from emptying the brake master cylinder. Vinyl vacuum caps, which can be found at most auto parts stores, make great temporary brake line plugs.
Inner axle seal. The old seal was removed and the seal surface
Next, the axle shaft is removed from the housing by loosening the four 14mm hex-head
nuts from behind the backing plate. Once the nuts are off, grasp the backing plate and
pull the entire brake and axle shaft assembly from the axle housing.
With the brake/axle assembly out of the way, the inner oil seal can be pulled from the housing end. Using your favorite seal puller or a large screwdriver, just pop the old one out.
Once you have the old seal out, check the seal surface and clean, if necessary. Also, clean any old gasket material from the axle flange, assuring none gets in to the axle tube.
The front hub socket, padded with a towel,
is perfect for driving in an inner axle seal.
The new seal should be prepared with a coat of grease on its outer surface
to help drive it in smoothly. Place the new seal into the axle end, and
carefully drive it in. For this seal, I found the front hub 2 1/8" socket with a towel on the end was the perfect size to drive the new seal. Once the seal is seated, coat the lips of the seal with grease. Next, clean up the axle flange surface and replace the O-ring, or use gasket-maker instead. If all you needed to replace
was the oil seal, you can now reassemble everything (see below), bleed the brakes, and you
Wheel Bearing Removal
Snap ring removal.
That was the easy part. Replacing the wheel bearing and outer seal is the more difficult part since the wheel bearing and its retaining collar are a press-fit onto the axle
shaft and you must remove the wheel bearing and backing plate in order to
replace the outer seal.
The first step is to remove the snap ring. A pair of heavy-duty "lock ring" pliers and maybe a pick or small screwdriver should do the job.
Now the bearing and retaining collar can be removed and there are a few different ways to go about it.
Using the press and the SST to remove the wheel bearing.
Home-made "Special Service Tool."
The "proper" method is to use a SST (Special Service Tool) and a press. SST's are
generally pretty expensive, however if you can cut and weld steel, this one can be made fairly easily. You can fabricate
one from scratch from some flat bar and a tube, or an even easier way is to make one out of an old axle housing, which is what I did.
The SST bolts to the bearing retainer/brake backing plate assembly using the original studs and nuts and then the whole thing is placed in the press. A few pumps later, the
bare axle shaft should drop free from the rest of the assembly. It is a good idea to place a block of wood or something under the axle to prevent damage to the
threads on the wheel studs when it drops. Now the SST can be removed from the backing plate, and the bearing can be tapped out of
Pounding the wheel bearing off using the shade-tree
Many people do not have access to a press or the means to build a SST, so there is also the "shade-tree mechanic" method of separating the wheel bearing from the axle shaft. This method can also be a little faster than using a press. You basically hold the assembly by the backing plate with the axle shaft pointing down (brake drum removed), raise it above your head, and slam the end of the axle shaft down on
the concrete as hard and fast as you can until the backing plate falls free of the shaft.
This may take quite a few hard hits, or if you are lucky, sometimes just a few. You
should leave all the brake parts assembled to the backing plate so that their weight is what is hammering down on the bearing and not just your hands. The more
weight on the backing plate, the easier the bearing will come off.
When using this method, be sure to wear some thick or padded gloves to protect your hands from the shock.
Something also needs to be placed on the concrete to prevent damage to the end of the axle shaft. I like to use Masonite since it is hard and dense enough to not absorb too much of the hammering force, but still soft enough to prevent mushrooming the end of the axle shaft. If you mushroom the shaft,
you will have to spend some time with a triangle file getting the splines back to where they'll fit
into the differential again.
Another way to get the retainer off is the way some factory service manuals show to do
it, which is by cutting most of the way through it with a grinder, and then using
a chisel to split it open and get it to release. You then still have to press or
hammer the bearing off. If you use this method, you have to be very careful not to nick the axle shaft. A nick on the axle shaft causes what engineers call a "stress riser," and can eventually
lead to axle shaft failure.
I have also heard that some people use a torch to cut off the bearing retainer. The heat from the torch can
undo the heat treat in the axle shaft, which weakens it. It is also very difficult to keep from nicking the axle shaft with the torch. For these reasons,
using a torch is not recommended.
Outer Seal Replacement and Axle Shaft Reassembly
Wheel bearing, bearing retainer, axle shaft, and backing
Replacing the outer seal.
Now that everything is apart, we can finally access the outer
seal to replace it and start putting things back together. You should be able to remove and install this seal by hand. Just
pop it out, push the new one in, and apply grease to the seal lip.
reassembly, place the backing plate onto the axle shaft, then the new wheel bearing, and
then the bearing retainer. Some bearings come with a new retainer, however mine
did not, so I just re-used the old one.
Hammering the wheel bearing and retainer back onto the
You can use a press to push the bearing and retainer
back onto the axle shaft, but it can be just as quick and easy to hammer them on. I've found that 2" steel tubing
with a 3/16" wall (2x2, 2x3, round, etc.), fits the bearing retainer and axle shaft just right.
Other people have found that common sizes of fence posts or steel pipe from the local
hardware store work as well. You just need something big enough to fit over the
bearing surface on the axle shaft and small enough not to slide past the
retainer. I prefer to use a small piece of this material to hold against the
bearing and retainer to keep them in place, and a larger, heavier piece over
that as my hammer. It is a good idea to place the axle flange on top of a vise or in a wheel laying
on the ground so that you are not pounding against the wheel studs. Pound the
bearing and retainer until they are fully seated and then install the snap ring.
the axle shaft and brake assembly and carefully guide the axle back into the
housing, making sure not to ride the shaft on the seal in the housing (which
could ruin the seal). To get the axle all the
way in, you may need to turn the axle shaft slightly to get the axle splines to line up with the splines in the differential. Install the 4 nuts on the inside of the backing plate and torque them to
51 ft/lbs. If your brakes were contaminated with gear oil, clean them thoroughly
with brake cleaner and consider replacing contaminated brake shoes. Apply new
grease to the brake adjuster and contact points between the brake shoes and
backing plate (for more information on rear brake maintenance, see the article
linked below). Also be sure to clean the brake drum before installing it. Reinstall the emergency brake cable and the brake line. Bleed the
brakes, check the differential oil level, and the repair is complete.
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