The first thing I did was loosen the wheel lug nuts and then placed a
floor jack under the center of the
I then jacked the car up until I could put two CBS building blocks; one
either side of the tunnel at the rear of the chassis. I then put
two short pieces of 2 x 4s on top of the blocks and under the
rear frame rails to
the rear of the chassis.
Place some rags on the frame under the axle so it doesn't contact the
and remove the jack. The axle should now be resting on the lower frame
Next I disconnected the rear universal joint from the rear axle. The
piece of wood and the string keeps the U-joint from falling on the
Note: My tunnel top cover is held on with #8-32 pan head screws. This
way I can easily remove it to get at the universal joint or do
coil-over shock springs were loose when the axle was lowered down to
the frame rails so I didn't have to disturb the spring adjustments. I
removed the lower mounting bolts and rotated the shocks out of the way.
I then removed the tires, drained the oil and started taking everything
else loose that held the rear axle in place. I didn't have to
remove the emergency brake cables.
In this picture I have removed the fuel tank and it's mounting
brackets, disconnected and capped the brake line and moved the rear
axle towards the rear until the pinion flange cleared the rear
Once the flange was clear of the bulkhead I rotated the axle to the
position in the picture.
The 2 x 4 is temporarily holding the pinion upright.
The shinny hoses are the FUEL lines. You don't want to starve
the engine do you?
After being convicted and hung ..... Oh wait, that's another website.
My method of keeping the rear end pinion upright is to use rope through
the link brackets on each end of the axle. The axle is resting on the
lower frame rail and wanted to rotate CCW in this picture.
To be able to remove the carrier from the axle housing you have to move
both axles a few inches outward to disengage them from the differential
The RX-7 axle doesn't use "C" clips on the axle ends. The axle bearing
retainers hold the axles in place.
This is the right end of the axle after I removed the brake
pads, disk rotor and
moved the caliper back into it's normal position.
Next remove the three bolts holding each axle
bearing retainer in place. They are located at the outboard ends of the
axle housing. Mine were rusted so badly I had to split the nuts to
The axle flange will
clear the caliper bracket while being removed.
You can see one of the CBS blocks and 2 x 4 at the rear of the chassis
by the suspension links in this picture.
The next few
picture are going to be somewhat difficult to explain but here's what's
If you are doing this job the Locost way you probably won't have the
Mazda tools like a slide axle puller.
To remove the axles you basically have to hammer them off. The axle
bearings on the axle shafts are pressed into the machined end
of the axle housing and they may be
stuck in place if they've never been removed before. Naturally, mine
were stuck. (REALLY stuck!)
A slide axle
puller hammers to PULL the axle/bearing out of the housing. It also
produces evenly distributed pulling power to the flange and bearing.
also hammer on the inside surface of the axle flange to PUSH the
axle/bearing out of the housing. The push is applied offset
to the center of the
flange but it does get the job done.
Since most Locosters aren't going to
have an axle puller, guess which method we are going to use?
The Locost approved axle removal kit. One 3lb hand sledge and
I first tried to use a ~18" length of 1" x 2" hard
and my special "convincing tool".
To remove the axle, you
place one end of the wood on the inside surface of the axle flange
on the other end of the wood. This did not work at first.
Machinists will tell you that you should not force anything.
hammer is OK though!
What actually was happening was that every
time I smacked the wood, the axle would move slightly and absorb the
force of the hit.
Once I realized what was going on,
I had to come up with some method of
holding the axle from moving. My solution is shown in the above picture.
The piece of wood on the left is resting against the
raised flange of the carrier. The piece of wood in the center is used
to fill the space between the left piece of wood and the piece of wood
on the right.
Another way is to use a longer piece of wood!
The angled piece of wood is resting against inside surface of the frame
rails in the area
What all the wood does is hold the axle from moving when
I hit the piece of wood applied to the back of the axle flange.. When
you get one axle out,
transfer all the wood to the other
side of the carrier and hammer away.
The hammer wood is threaded through the ropes so one end is resting
the inside surface of the axle flange. You pound on the other end of
the wood from inside the boot. It's going to take 4 or 5 really
hard hits to remove a stuck bearing.
As soon as you see the bearing starting to move out of the axle
lighter hits so the axle
doesn't fly out. Hold the axle flange up with your third hand as the
bearing comes out of the
housing so the axle doesn't lay
on the oil seal.
I removed the axles completely so I wouldn't have to
tie them up
away from the seals. And I wanted to inspect the wheel bearings anyway.
Next remove the bolts holding the carrier to the axle housing
lift the carrier out of the housing. It weighs ~50 lbs so be careful.
This picture shows the RX-7 carrier resting in the Locouki special
"carrier support structure". That's the four pieces of wood that keep
the carrier from falling to the bottom of the "carrier holding fixture"
(the white 5 gallon plastic bucket).
Hey, you want Lo-cost?
This is how you do it.
I use two pieces of hard wood under the flange to support the weight
of the carrier.
Two thin pieces of plywood are used to hold the weight
pieces of wood in place. Small finishing nails hold the whole
The tag in this picture is the backlash in 1/1000 of an inch after I
had adjusted it (.00275"). The backlash was ~.007" when I started. (WAY
how do you hold the pinion from moving while checking
you have the carrier sitting on top of the bucket look how far
down into the bucket the pinion is. Next make a slot in the side of the
bucket so a pair of grip pliers can be inserted through the slot to lightly
clamp the pinion flange so it can't rotate when taking measurements.
slot should just be wide enough so the pliers can fit through the slot
but not move left or right. I made the slot by drilling a vertical
row of 1/2" holes with a wood drill. I then used the drill to
remove the material left between the holes.
spring is used to
make sure the pliers don't move and also to hold the pliers in the slot
when they aren't clamped on the pinion.
that your expensive pinion adjusting fixtures are ready ..............
There are three tools you can't
skimp on and must have to work on an early RX-7 rear end;
1. A good dial indicator and the clamp to hold it in position.
2. A torque wrench.
3. A 7" to 8" micrometer. (I made my own!)
In this picture I am measuring what I call the CCW diagonal
measurement. You should also do the CW diagonal measurement.
How to do the measurements are explained below the last picture on this
page. Basically I
wanted to set the rear end BACK to the factory setting when I was
I made my 7" micrometer from some 1/2" thick aluminum stock I had. The
three pieces are held together with flat head machine screws. Getting
the pieces at right angles is very important to get accurate readings.
The micrometer head was part of a World War II "X" band microwave
guide tuner. I've been planning on using it for something all these
years. It's removable in case I need it for something else. My junk
collection goes WAY back!
I keep the micrometer away from temperature changes while using it so
aluminum bar doesn't change length between measurements.
That includes NOT touching the long bar of the micrometer between the
Before you loosen the four bearing
measure the distance between the "pilot sections" on the bearing
caps with your micrometer. Write the data down, you can use it later to
set the preload.
The shiny spot near the right bearing cap bolt is one of the "pilot
sections" (a Mazda term) that you use to measure the bearing preload.
The next set of pictures (below) illustrate how to do this measurement..
You can see the other pilot section on this bearing cap near the left
side bearing cap. There are matching pilot sections on the other
Notice that the dial indicator is contacting the gear tooth at the
required 90° angle. It really doesn't matter where around the ring gear
you place the dial
indicator as long as you use the same position for all four of the 90
readings around the ring (crown) gear.
This picture shows my Locost version of the special Mazda
"differential wrench" p/n 49 0259 720. Locosters can use a
hammer and a
diameter flat ended punch.
Move the dial indicator OFF the gear tooth before hammering on the
First loosen the four bearing saddle bolts and then set them to about
1/3 their rated
Use the punch to rotate the threaded adjusters the
amount and in the same direction to move the ring gear back and forth.
This sets the backlash.
You don't have to use a lot of force at this point, you barely want to
move the adjusters.
I used a center punch to mark both bearing adjusters and caps
BEFORE I adjusted the backlash. The punch marks were next to each other
before I changed the adjuster position.
The dividers now are resting in the two
punch mark holes (after the adjuster was rotated to correct the
and shows how much I had to rotate the adjuster to move the
backlash ~.004". The divider is used to make sure
that each adjuster is moved the same
As you can see, it doesn't take much rotation
of the adjuster to move the gear a lot. (.004" is a LOT when you are
setting backlash.) The adjusters are right hand thread.
The adjuster in this picture was rotated CCW. Therefore the other
should ALSO be rotated CCW when viewed from this direction through
the spool. That would
move the all the parts including the ring gear, towards the camera and
the pinion. CCW rotation results in LESS backlash.
Start with about 1/4" of rotation and recheck the backlash the first
time around. This will give you an idea of how much things move.
I found that as I tightened the bearing cap bolts to 2/3 of the
required torque that the backlash was reduced by a few tenths of a
thousandths. If you are near the lower backlash tolerance, you have to
this into consideration.
This picture clearly shows the two flat spots on either side of the
divider which are the "pilot
sections". Those are the places where your micrometer touches while you
measure diagonally from side to side
while setting the preload on the spool bearings. The other bearing cap
has the same pilot sections.
Taking the CCW diagonal measurement while setting preload.
The next job is to set the
preload. This is done by very carefully and EQUALLY rotating the
adjusters inward or outwards. In affect the bearings are squeezed
together so they are under pressure (or "preloaded"). If you don't
rotate the adjusters equally, the backlash will
You will have to remeasure
the backlash at 90 degree points around the ring gear to make sure it
Are you wondering how you know when you have enough preload on the
bearings? That's where the 7" micrometer comes into play.
On the 1st generation Mazda RX-7 and 1994 to 1997 Miatas you tighten
the bearing adjusters until the diagonal pilot section measurements are
between 7.3004" and 7.3033". Yep, +/- 0.00145" thousandth
Since my micrometer is homemade I couldn't be sure of the absolute
reading within a few thousandths of an inch. (I did a transfer
calibration by using two 4" dial calipers.)
Measuring the diagonals BEFORE I loosened the bearing
mount bolts was a method of checking the micrometer.
My initial measurement, before I loosened the bearing bolts was within
the +/- tolerance. At that point I had more confidence in the
I then set the diagonal measurements as close as I could to the
original numbers. (You did write them down before taking
things apart didn't you?)
Taking the CW diagonal measurement.
Here is how I take a micrometer measurement.
First, wipe off any oil from the surfaces to be measured. You want to
be able to feel the friction of the micrometer anvils sliding on the
Notice that the left hand is holding the stationary micrometer anvil
against the far side pilot section and the base of the micrometer is
resting on my right hand to support it. My right fingers very
gently turn the measuring head to take the measurement.
You do NOT want to -tighten- the micrometer. You
movable anvil to just graze the pilot section. As you move the
micrometer back and forth, you can feel (and hear) the movable anvil
gently sliding across the pilot section when you have the setting
Once the preload is correct, recheck the backlash and if
correct, torque the bearing saddle bolts to the rated torque.
all of this is a lot of work, just remember that I didn't do the pinion
setting and pinion preload adjustments. My gear wear
patterns are very good so I just left things as they were.
Now you know why the good shops want $100/hr to do this. I was recently
quoted $500-$600 to do this job. Since I was able to do the adjustments
in one day at a leisurely pace I figured I came out pretty good for a
If you aren't sure YOU can do this, figure that after building a whole
car are you going to let a few thousandths
of an inch bother you? Besides how many people do you know that can set
a rear end? Join the crowd!
As usual Mr. Phelps, if you or any of your helpers are apprehended
this job incorrectly, the Dept. will disallow any knowledge of your
smoke! But this is what can happen if YOU smoke!