Replacing worn-out front wheel bearings, GM 4wd truck.
GMC / Chevy Truck 4x4 Driveline Repairs:

Replacing Worn Front Wheel Bearings
On A 1999 GMC Jimmy

This Article May Also Apply To Full-Size GMC and Chevy K1500 Pick-Ups, Chevy Tahoe, Suburban and GMC Yukon


In This Article:

The axle nut is loosened while the car is on the ground. The vehicle is raised, the wheel and brake caliper moved out of the way, and the axle nut is removed. The front hub bolts are removed and the hub is pried away from the steering knuckle. The ABS sensor wire is disconnected and the new hub is installed.

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Skill Level: 3-4 (Intermediate to Advanced) Time Taken: About 4 Hours

By Bruce W. Maki, Editor


About 6 months ago my wife's 1999 GMC Jimmy developed a noise while driving at highway speeds. It sounded like an airplane about to take off. Actually, I thought the sound was kinda cool, but my wife found it a bit embarrassing.

Based on the rumbling noise that I heard when driving straight and turning the steering wheel, I suspected that the front right (passenger side) wheel bearing had gone bad. Front wheel of 1999 GMC Jimmy with bad wheel bearing.

The front driveline on many 4 wheel drive light trucks is essentially the same as a front wheel drive car. I have had two other front wheel drive cars that developed a bearing noise, but the noise on those cars was more of a "groaning" sound than a propeller airplane. My experience with front wheel drive bearings has been that the car can go a few months with failing bearings, as long as the car steers normally and the wheels don't feel at all loose when I push and pull on the top and bottom (while raised up). Of course, any looseness could also indicate a worn-out ball joint.

When you try wiggling a raised wheel from side-to-side it will move because the steering linkage is moving.


I don't recommend driving a car with a bearing that is making noise. There is always a chance that the bearing could get much worse and I suppose the wheel could possibly fall off, which could cause a serious accident. If you choose to drive a vehicle with a bad wheel bearing, that is your decision, and you assume responsibility for any consequences.

After a couple of months I could hear the noise at lower speeds, as low as 15 miles per hour. I knew the problem was getting worse.


Diagnosis: Bearing Failure...
But Which Side?

When a vehicle makes a groaning or rumbling sound that varies with vehicle speed and not engine speed, I first suspect wheel bearings that have worn out. But determining which side is making the noise isn't always easy.

I would hear the "airplane" noise when the car was going straight or making a left turn. The noise went away (or was less) when making a right turn. On a right turn the left (driver's side) front wheel is pushing inward, and the right wheel is being pulled away from the car, so bearings are experiencing less "thrust".

A couple of weeks before doing this repair I raised the front end of the car, removed both front wheels and unbolted the brake caliper/bracket assemblies. First I used a pry bar to pry each hub outward to check for any free play. I found none. I tried wiggling each hub up and down to check for play, but there was none. I turned each axle by hand while listening for noise. None audible. However, when I rotated the right-hand hub I could feel a very slight "bumpiness" that I didn't find on the left side. THAT was the symptom that assured me that the right side was the problem.


Replacing The Front Wheel Bearings and Hub

Front wheel with wheel chocks, removing hub cap to reach axle nut. I placed wheel chocks on both sides of the tire and used a big flat screwdriver to remove the hub cap.


I had to buy one special tool for this repair job: a 36mm axle nut socket. This 1/2" drive impact socket cost $19 at my local NAPA auto parts store. This socket is deep enough to accommodate the part of the axle that sticks out beyond the hub nut. 36mm axle nut socket for GM truck.


Applying penetrating oil to axle nut. I applied some penetrating oil to the axle threads in front of the hub nut.


I put the socket on my impact wrench and tried loosening the axle nut. I wasn't sure if my impact wrench would be able to remove this nut, but within a couple of seconds the nut had rotated a quarter-turn.

Sometimes it's hard to see the impact socket turn, so I used a permanent marker to mark the top of the hub nut. That way I could just pull the socket away and see how much the nut had turned.

Loosening axle nut with impact wrench and 36mm socket, GM truck.


Removing front wheel with impact wrench.

Then I raised the front end and supported the car on jack stands.

I removed the wheel with my impact wrench and a 3/4" impact socket.

If an impact wrench is not available, the lug nuts must be loosened before the car is raised. Otherwise the wheel will rotate when the lug nuts are turned.


Unbolting The Brake Caliper:

The brake caliper needs to unbolted and hung safely out of the way with mechanic's wire or bungee cords.

There are several fasteners on the back side of the brake caliper.

Only the brake bracket mounting bolts (B) need to be removed for this repair. I removed these bolts with an 18mm box-end wrench.

In case you are curious... The bolts marked "A" are the caliper slide pins. "C" points to the brake line connector.


Labeling of fasteners on GM truck front brakes.


Pushing brake caliper back with C-clamps.

Oops... I almost forgot. Before I could lift the caliper and bracket off the steering knuckle, I had to push the caliper back with a big 6" C-clamp, similar to what is shown in this picture.

Actually, I only used one clamp. This picture is from our article about replacing front brakes on this 1999 Jimmy, which provides more details about working on the front brakes.


I used a 34" long bungee cord to support the caliper. The bungee cord is wrapped around the shock absorber tower. A bungee cord about 3 to 6" shorter would've worked even better.

It's important to make sure that the caliper does NOT simply hang on the flexible brake line. That can damage the brake line.

Hanging brake caliper with a bungee cord to move it aside while working on front hub.


Removing front brake rotor on 4WD GM truck. I removed the brake disc (rotor). It simply slid off, but sometimes the rotor can be stuck to the hub from corrosion. In that case it may be necessary to tap the rotor carefully with a hammer.


Then I removed the hub nut with the impact wrench and 36mm socket. This nut did not spin easily... I'm guessing that they designed the threads so the nut would be self-locking.

There was a big flat washer behind the hub nut, which I removed.

Removing axle nut to repair bearing, GM truck.


Front hub mounting bolt locations, GMC Jimmy  or Chevy Blazer.

There are 3 bolts that secure the hub to the steering knuckle. The heads of the bolts are towards the inside of the vehicle... the ends of two of the bolts (red arrows) are visible here.

I sprayed some penetrating oil on the ends of the 3 bolts.


I turned the steering wheel to gain access to the top and rear bolt heads. Front hub bolt locations on GM truck.


Using wrench and hammer to remove hub bolts.

To remove the hub mounting bolts, I used a "poor man's impact wrench", which is simply a box-end wrench (18mm in this case) and a dead-blow hammer to pound on the end of the wrench.

Given that these bolts are supposed to be tightened to 133 foot-pounds, I was surprised that the bolts came out without a fight.


Then I turned the steering wheel the other way to expose the front mounting bolt.

Location of front hub bolt, GM truck.


Removing front bolt on front hub, using breaker bar and socket.

I wasn't able to turn the front bolt with a wrench, and I couldn't fit my impact wrench in the tight space, so I used an 18mm socket on a 1/2" drive breaker bar to loosen this bolt.

Once the bolt was loosened, I used a ratchet with a 2-1/4" extension to remove the bolt. Without an extension the head of the ratchet wouldn't fit next to the CV joint.

These bolts didn't unscrew very easily because they had thread-locker compound on them.

Note that some GM trucks and SUV's may use 4 bolts to fasten the hub to the steering knuckle and the removal procedure may be different.

To separate the hub from the steering knuckle, I hammered a screwdriver between the hub and the knuckle (arrow).

This is not an ordinary screwdriver... I call it a beatin' screwdriver, which has a shaft that goes all the way through the head, and a metal cap on the end. If I used a normal screwdriver with a plastic handle (and no metal cap on the end) the handle would just break.

These are cheap screwdrivers... many years ago I bought several for less than a buck each.

Separating front hub from steering knuckle on GM truck.

Once the splash guard (between the hub and knuckle) was loose, I knew the hub was separated.

Front hub after being separated from the steering knuckle.

With a little more prying (and tapping on the end of the axle shaft) the hub completely separated from the steering knuckle.

However, the center of the hub was still attached to the axle (the shaft has splines that engage the center of the hub).

I sprayed some penetrating oil into the splines around the shaft, just beyond the ends of the threads.


I used this cheap-a$$ 2-jaw 4-inch gear puller to pull on the hub while pushing the axle inward.

I didn't expect this to work at all, but to my surprise the hub came off. I suppose all that penetrating oil and tapping (more like beating) on the axle loosened up the splined connection.

Using a gear puller to remove front hub from drive axle, GM truck.

There was just one more task... disconnecting the ABS sensor wire.


Disconnecting The ABS Sensor Wire:

The new wheel hub assembly included the ABS (anti-lock brake system) sensor and a long wire with a connector.

ABS sensor wire, front wheel, GM truck.

The ABS sensor has a long wire that runs into the engine compartment. The arrows point to the ABS wire.

There were three brackets to remove.


1: The mounting location of the first bracket (which I had already removed). This required a 10mm socket.

2: Second bracket, which required a 13mm wrench to hold the bolt head on the inside of the upper control arm, and a 13mm wrench (or socket) to remove the nut.

3: Third bracket, which required a 13mm socket.

4: ABS sensor wire.

Brackets 2 and 3 needed to be re-used. The new hub includes bracket 1.

ABS sensor wire bracket locations, GM truck, front right.


ABS wheel sensor connector, front, GMC Jimmy.

The ABS sensor wire connector (arrow) is barely visible in this picture.

This is located in the engine compartment, below and to the right of the battery (when viewed from the front).


Once the ABS wire was released, I pulled the hub off the axle.

I handled the axle carefully, making sure not to damage the splines or the rubber boot around the CV joint.

Front wheel bearing hub after removal, GM SUV's and trucks.


Lip in steering knuckle where hub attaches.

One possible source of grief: There is a lip around the circular opening, and the hub fits inside this lip. But there was some rust on this surface, and I figured this could create some interference when the new part is installed.

I removed the rust with the tip of a file, by scraping around the rim in a circular motion. Then I blew the dirt out with compressed air and a blow gun. I cleaned the dust from the axle splines with a paper towel and brake parts cleaner.


The new hub assembly came with the ABS sensor and wire. It also included 1 of the 3 brackets needed (arrow).

The instructions say that the old sensor cannot be re-used because it's not compatible with the new hub. The second and third brackets need to be installed on the wire on the new hub.

Old front hub compared to new hub, GM truck.


Green marks on ABS wheel sensor wire to indicate position of clamp brackets. There were green marks on the new wire where the old brackets needed to go.


Before installing the new hub, I applied a thin coating of copper-based anti-seize compound around this part of the hub, where the hub fits tightly into the steering knuckle. New front hub and bearing with anti-sieze compound.


End of axle shaft with anti-sieze.

I also applied some anti-seize to the splines on the axle. This should make these parts easier to remove in case I need to remove the bearing or axle later.

It's possible that a constant-velocity (CV) joint may need to be replaced someday, and this connection would need to be taken apart.

Note in the above picture that I cleaned up the mating surfaces on the knuckle. I used a die grinder and a Roloc disc to do this.

I used a wire wheel to clean up the threads on the hub mounting bolts.

The white stuff on the bolts is probably some type of thread-locking compound. I applied some medium-strength thread-locker to the cleaned-up bolts.

Hub mounting bolts.


Installing The New Hub:

Installing new hub by pushing inward with knee.

Installing the new hub wasn't easy because the axle sprung outward when the old hub was removed.

I had to push the new hub inward with my knee (wearing knee pads helped) while I got the lower bolts started in their holes.


Oops... I forgot to install the splash guard first. So I had to remove the hub bolts and put the guard in place. Installing brake splash guard before front hub.


Installing front hub properly, with splash guard in place.

I installed the hub again. I could only get the bolts threaded in a few turns, because the axle shaft was pushed so far back.

So I using my impact wrench and 36mm socket, I installed the hub nut part way. This pulled the axle outward and let me finish threading the hub mounting bolts by hand.

Then I turned the steering wheel to gain better access to the mounting bolts, and I tightened them very tight. There was no way I could reach these bolts with my torque wrench, so I just used a dead blow hammer to pound on the 18mm box-end wrench.

Then I used the impact wrench and 36mm socket to tighten the hub nut most of the way.

Next I attached the cable brackets to the car. The second bracket was kinda tricky... I found it best to put the bolt through the hole in the bracket and then push the bolt through the brake hose bracket and through the upper control arm.

Connecting the electrical connector was a total hassle. There was only enough space to get one hand down there. After a lot of struggling I finally got the wires connected.

Then I replaced the brake rotor and brake caliper. Before putting the rotor back on, I applied a thin layer of lithium grease to the face of the hub, so the mating surfaces don't rust and cause the rotor to stick to the hub. I tightened the brake bracket mounting bolts with an 18mm wrench. These bolts need to be pretty tight, probably similar to the 133 foot-pounds required for the hub mounting bolts.

I replaced the wheel and lowered the car. Then I tightened the wheel lug nuts with a torque wrench to 100 foot-pounds, which I understand is a typical torque requirement for light truck lug nuts.

I chocked the wheel again and put the 36mm socket on my torque wrench. The scale on the wrench only goes up to 150 foot-pounds, and the torque requirement in 165. But I just turned the dial another one-and-a-half turns and tightened the axle nut until the wrench clicked. Just to be sure, I used the impact wrench to turn the axle nut another 10 to 15 degrees.

I replaced the hub cap and took the car for a test drive. The "airplane" noise was gone.

Cost Of This Repair:

I paid just under $80 for the new hub assembly at my local NAPA auto parts store, and $19 for the axle nut socket. My total cost for this repair was $99 plus sales tax. If I didn't already have the copper-based anti-seize and the thread locker I would've spent another 10 to 15 bucks.

An independent auto repair shop quoted me a price of $336, which included $235 for the aftermarket part, and 1.3 hours of labor at $78 per hour. I know repair shops mark up the price on parts, but that seems kinda steep. Knowing that parts and labor at new-car dealers are higher than independent shops, I don't even want to know what my local GM dealer would charge for this repair.

I saved over $200 in one afternoon. It pays to be handy.

Update: About 5,000 miles later, the other front wheel bearing starting making noise, so I replaced it too. The mileage on the car was about 165,000 at that time. I suppose it makes sense to replace the wheel bearings in pairs, if you have the money.

More Info:

Special Tools Used:

  • 36mm Axle Nut Impact Socket, 1/2" Drive
    NAPA Part 775-9022 ($19+tax)
  • 4" Gear Puller, 2-Jaw (3-Jaw Preferred)
  • 1/2" Drive Click-Type Torque Wrench

Tools Used:

  • Wheel Chocks
  • Pneumatic Impact Wrench
  • Air Compressor
  • Floor Jack
  • Jack Stands (2)
  • 6" C-Clamp
  • Bungee Cord, 34" Long (Slightly shorter cord may work better)
  • Sockets: 3/4", 18mm, 13mm, 10mm
  • Wrenches: 18mm (1/2" Drive), 13mm, 10mm
  • 1/2" Drive Extension, 2-1/4" Long
  • 1/2" Drive Breaker Bar
  • 1/2" Drive Ratchet
  • Assorted Pliers
  • Dead-Blow Hammer
  • Air Blow Gun
  • Large Flat Screwdriver With Full Shaft
  • Large Ball-Pein Hammer
  • Air Die Grinder With Roloc Disc
  • File

Materials Used:

  • Wheel Hub Assembly, (Right Side),
    NAPA Part No. PBR930097 ($80+tax)
  • Penetrating Oil
  • Thread-Locker, Medium Strength
  • Copper-Based Anti-Seize
  • Lithium Grease
  • Automotive Brake Parts Cleaner

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Written January 2, 2009