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Rear Wheel
Bearings
By Ron Bramlett
(From our February 2000 Newsletter) |
Page 1 | Page 2
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| In the last issue of the Mustangs Plus
Newsletter, we went over front wheel bearings. In this issue,
we're going to finish up with rear wheel bearings. Then, in our next issue, we're going to
take a look at rear end assemblies. We'll show you how to
tell an 8" from a 9", a posi from an open, and how to check gear ratios. We'll
even get into rear disc brakes vs. rear drum brakes and help you decide which is better
for you. Now, on to Rear Wheel Bearings. Rear wheel
bearings are not nearly as complicated as front wheel bearings and we tend to not think
much about them. But there are a few things worth going over because the rear wheel
bearings do more than just allow the tire and wheel to go around and around. They also
keep the rear tires and wheels on the car!
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| On our classic ‘65 to ‘73 Mustangs, the
front wheel bearings do not hold the tire and wheel on the car. That job is done by the
nut and cotter pin on the end of the spindle. Not true on the other end of the car!
A rear wheel bearing failure can result in much more loss than just the cost of a bearing.
The rear wheel bearings and their retainers are the only things which hold the rear tires
and wheels on the car. If a rear wheel bearing comes loose or if the bearing comes apart,
the axle can slide right out of the rear end with the brake drum, tire and wheel attached
to it! This can be quite dangerous as well as expensive. So we need to make
sure our rear wheel bearings are always in good shape and up to the job. |
|
New rear
wheel bearings with their respective retainers. Our Classic Mustangs all came from
the factory with the smaller diameter rear wheel bearings as shown on the left.
However, due to rear end swaps, it's possible to find them now equipped with the larger
style as shown on the right |
|
Our Mustang's rear wheel bearings are what's called a
"sealed bearing". Sealed bearings are used in many places on our Mustangs
besides the rear wheel bearings. Bearings for accessories such as alternators, air
conditioning pulleys, and heater motors are good examples of sealed bearings. What this
means is that the bearing and the grease the bearing needs to keep it lubricated during
use are all sealed together as a unit. You never have to service it. If, for some reason,
it loses its lubrication, you simply replace it.
|
| This brings up an interesting point. Many people are
under the wrong concept about how the rear wheel bearings are lubricated. They assume that
the gear oil from the rear end also lubricates the rear wheel bearings.
This is not true. The axle housing has a grease seal in each axle tube. The axle itself
has a machined journal for this seal to ride on. The purpose of this seal is to keep the
gear oil from getting into the area where the rear wheel bearing rides. But many people
are confused because Ford uses rear axle flange gaskets for the axle retainers.
The axle retainers are the flat plates with the four holes in
them that bolt to the axle housing and hold the rear wheel bearings in place. In fact,
Ford has two of these gaskets per side. One for the rear brake backing plate and another
for the axle retainer. The backing plate is sandwiched between the rear axle housing and
the axle retainer and has these gaskets on both sides. These gaskets are designed to keep
the brake dust out of the bearing, not to keep gear oil in. But I've seen people change
them, even use silicone on them, to stop gear oil from leaking onto their rear brakes. Of
course what they actually need to change is the axle seal.
If you look closely at the bearing retainer plates, you'll see
that most of them provide a vent to the outside for the bearing. This means that even if
you silicone all around the gaskets, if the axle seal is leaking, you will still have gear
oil getting on the rear brakes! So remember. These gaskets are for keeping something out,
not keeping something in. Can you reuse these gaskets if you want? You bet!
|
| Now, on to the rear wheel bearing itself. When you buy
a new rear wheel bearing, it has two parts. The actual rear wheel bearing and a ring of
metal which is called the bearing retainer. If you were to take the rear wheel bearing
apart, what you would find is an inner and outer race, several ball bearings, grease, and
two thin plates which are the grease retainers. The inner and outer races are grooved for
the ball bearings to ride in. This allows the bearing to be loaded from side to side, such
as when your car goes around a turn, and not to have the inner race pull away from the
outer race. The rear wheel bearing and the bearing retainer are
pressed onto the axle. Since this requires the use of a hydraulic press, which most people
do not have access to, this job should be done by a competent shop. I say competent shop
for a couple of reasons. You only get one shot at pressing on a rear wheel bearing and
retainer. Once the bearing and the retainer have been "stretched" onto the axle,
they're meant to stay there. If they're pressed off and then on again, they will go on
easier the second time and not have the holding power that they're supposed to. |
|
This photo shows a small
bearing axle with the axle retainer, wheel bearing, wheel bearing retainer and the
machined area that the oil seal rides on. You can tell exactly where the seal rides
by the shiny area around tthe axle. This is the style of axle that our Classic
Mustangs came from the factory with. |
|
| I've seen people press on the bearing and retainer and
forget to insert the retaining plate between the bearing and the hub end of the axle. In a
case like this, the "new" bearing which has just been installed, is now junk.
Since these bearings are made to press on one time and one time only, if you have to
remove a new bearing and retainer from the axle, even if it has never been used, you might
as well throw it in the garbage. So it goes without saying
that you never take a rear wheel bearing off one axle and put it on another.
(continued on page 2) |
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