Fiero Rear Hub Replacement Procedure

[Fierofool]

84-88 Pontiac Fiero Rear Hub Installation and Torque

After removal of the brake caliper using a Nr. 50 Torx bit or hex wrench as applicable.  Some replacement slider bolts are hex head cap bolts.  Verify which with a mirror before proceeding.

Do not push the piston back into the bore as damage will occur.  The caliper will slide back onto the disk at installation time.  Remove the disk, old hub and seal and dust shield.  Make note of the depth of installation of the old seal in the back of the spindle before removing the seal.  Vernier Calipers are a blessing in this operation. 

A good heavy duty screwdriver inserted through the hub flange will help to keep the assembly stationary while you break the hub nut loose.  Discard the hub nut and use a new one at time of installation.  Keep the hub nut washer.  It’s reusable and generally doesn’t come with a new hub assembly.  They’re also hard to find, sometimes. 

Using a length of 2 inch PVC pipe, place a coupling on one end and a cap on the other.  The coupling is the perfect size to drive the new seal into the spindle and the cap gives a good surface for striking with a rubber mallet or dead blow hammer.  This is what I made using The Ogre’s design.



 

If you have a set of Vernier Calipers, use the depth probe to measure the depth the seal is set into the spindle, once you have removed the hub from the spindle.  Record the measurement.  It's important that the new seal be set at the same depth.  Push the axle back into the transmission to give room to knock the old seal out the back.  Drive the old grease seal out using the PVC installation tool.  You will need a good pair of side cutters to cut the seal for removal from the axle stub.  Otherwise, you may need to separate the rear ball joint and swing the knuckle out of the way.  Or you may be able to crush the seal down small enough to pull it out through the front.  If you don't have Vernier Calipers, don’t discard the old seal.  Look at the outer metal shield and note the depth the seal protruded out the back of the spindle bore.  There will be a difference in color around the metal shield.  You should install the new seal to the same dimensions.

The new seal installs from the front with the open side toward the transmission.  Be sure the spindle bore is clean.  You may need to give a light burnish with an emery cloth or sandpaper to break any rust or glaze that’s formed.  There is also a drain hole on the lower surface of the bore.  Be sure it’s clear. 

Put a very light film of chassis grease on the inside of the spindle bore and place the seal into the bore and slowly tap it into the spindle.  The coupling acts as a guide for driving the seal straight.  Check frequently to be sure your seal is seated to the same depth as your old seal.  If you drive it too far you’ll need to separate the ball joint to get the new seal off the axle stub without destroying the seal.

Once installed, fill the seal cavity with bearing grease.  This is the area where the CV joint axle flange seats inside the seal.

Install the O-ring on the back of the hub in the area indicated by the red in the diagram on the last page of this document.  You can put a light film of lubricant on it if you desire.  Synthetic brake grease would be good.  Smear about 1 gram of chassis lube inside the bore.  This helps to prevent rust and catches fine dust that may enter through the drain hole. Keep lubricant out of the drain hole.

Install the dust shield and carefully offer the hub assembly up to the spindle to avoid damaging the O-ring.  Orient notches in the hub assembly to match the old imprints on the spindle. 

You may want to use a thread locker.  Blue LocTite in the amount of 1-2 drops on each bolt is sufficient.  Also, put a small amount of Anti-seize on the axle splines, only.

Snug the 3 dust shield mount bolts with a wrench or ratchet.  Torque the 3 bolts to 55-70 ft. lb.  I like to go midway at about 63 ft. lb.  Thread lockers will actually yield a slightly higher end torque due to their lubricating nature. 

Torque the hub and bearing mount bolts to 63 ft. lb.

Install the washer and axle nut.  Always use a new nut.  If for any reason you need to remove the nut, purchase a new one.  They are one-time-use nuts. 

Again, you can use about 2 drops of Blue LocTite thread locker on the axle threads if you desire.

Do an initial torque of the axle nut to 75 ft. lb.

Install the disk and brake caliper and hook up the emergency brake.

Remove the wheel center cap and install the wheel.  Tighten the lug nuts to 100 ft. lb. 

Lower the car to the ground.  Do not roll the car for even a short distance.  You stand a good chance of destroying your new hub assembly bearings.

Block the wheel on each side.  Retorque the axle nut to 200 ft. lb. 

Install the wheel center cap.  You may want to recheck the hub nut torque after 200 miles, but it really isn’t necessary.









 

[GTRS Fiero]

What happens, if you don't install #4?

[Fierofool]

That seal keeps dirt and water out of the bore where the bearings are housed.  It leaves about a 1/4 inch gap all the way around the CV joint flange. 

[GTRS Fiero]

The axle wouldn't set with that seal in place.

[Fierofool]

I can think of only 3 reasons.  1.  Wrong axle.  It may have had an ABS reluctor wheel on it?  2.  The seal was driven in backward.  3.
 The seal was driven into the bore too far and the CV joint flange was pressing against it.  If the clearance is too tight, the flange will cut through the seal in short time. 

What you are viewing is the inboard side of the knuckle.  The seal is driven in from the left and the cavity of the seal is facing to the right in this image. 

[GTRS Fiero]

Everything was together, but the boot was leaking.  We removed the axle to fix the boot.  The seal was not removed.  The axle was reinstalled.  I went for a drive, and the car about swapped ends when it shifted.  Nothing was visibly wrong.  We pulled the axle again.  We couldn't get it back together.  The axle was fully into the transmission.  We removed the seal, and then everything went back together, and the Fiero drove correctly again.

[Fierofool]

Sometimes the spring inside the transmission axle seal will come out when the axle is removed.  Then it gets on the output shaft and won't let the axle go all the way into the transmission. 

Did you do the initial torque on the axle nut before setting the car down on it's wheels?  The axle should have been inside the spindle enough that you could do this? 

How far would it go back together?  How much did it lack? 

[GTRS Fiero]

.25" too far out.  Hmmm.  Maybe the spring on the transmission seal is still out.

[TopNotch]

There are a few minor differences between the above procedure/diagrams when you are doing an 88 Fiero, but it's basically the same.
And I've given this tip before -- to torque your axle nut to 200 foot-pounds, if you weigh 200 pounds, stand one foot out on your breaker bar. Adjust your standing point as needed for different body weights. No torque wrench needed for this nut.
If you absolutely positively can't find a new axle nut (happened to me when I had to take the nut off my wife's 2001 Ford Escape), you can make do with the old one if you properly prepare it. The reason you need a new nut is that the old one was slightly flattened out of round to make it stay put. Figure out which sides were pushed in on the old one, and use a hammer and punch to add a little more flattening.
And about pushing in the caliper piston -- you shouldn't need to do it anyway unless you're changing pads. You actually can push it in if you remove the parking brake lever and then screw the parking brake screw in a little before pressing on the piston. The direction to turn the parking brake screw in order to screw it in will be different depending on which side of the car you are working on.

[GTRS Fiero]

How does it get flattened?  It's just tightened with a wrench.

[Fierofool]

They are swaged nuts.  If you look around the facets of the nut, you might see a small dimple.  This indentation pushes the internal threads of the nut in a fraction, tightening the grip on the thread of the bolt or shaft onto which it's installed.  Usually the metal of the nut is slightly softer than the bolt or shaft to prevent damage to the bolt or shaft threads.  It actually damages the threads of the nut when it's installed.  That's why it's a one time use nut and should be discarded when removed.  Cheaper to replace the damaged nut than the damaged axle shaft.  You might succeed in swaging the nut yourself, but you may also succeed in damaging your axle threads.

I strongly suggest that you get another nut and a new seal and make sure it's properly installed.  Else dirt and water will enter around the back of the axle splines and into the back of the bore and bearing. 

In this photo of the rear of a Fiero rear hub, taken from RockAuto.Com, you can see the bearing seal inside the hub.  The axle seal is to the upper right and that's what you have eliminated.  It's inserted into the back of the knuckle bore to keep the bore clean.