The Chevrolet Trailblazer was introduced in 1999, as an upgraded version of the Chevrolet Blazer. The Chevrolet Blazer was sold alongside the Trailblazer until the Blazer was discontinued after the 2005 model year. The base 2004 Chevrolet Trailblazer LT was equipped with a 4.2-liter, in-line six-cylinder engine that produced 285 horsepower. The 2004 Trailblazer LT was a rear-wheel-drive vehicle. The hub bearings on the 2004 Trailblazer LT are located behind the brake rotors, mounted onto the face of the steering knuckle. Wheel bearings on this vehicle should be replaced by someone with prior mechanical knowledge.
Turn the ignition key to the "II," or accessories, position, so the dashboard lights come on. Make sure the steering wheel is unlocked and turning freely, though it will be hard to turn without the engine running. Leave the wheels turned straight forward, and exit the Trailblazer.
Loosen the front wheel lug nuts with a tire iron on the side you are doing to work, but do not remove them yet. Raise the front of the Trailblazer using a jack. Place jack stand beneath both front frame rails on either side of the truck. Lower the vehicle onto the jack stands. Remove the front wheel lug nuts completely, then remove the wheel from the side you are going to replace the bearing on.
Insert a small pry bar through the hole in the caliper housing. Pry the inside brake pad (behind the rotor), so that it moves away from the rotor slightly. Remove the caliper mounting bracket bolts, which are located behind the brake rotor on the knuckle assembly. Use a 1/2-inch drive breaker bar and socket to remove the bolts. Pull the caliper and caliper bracket off of the brake assembly. Hang the caliper and bracket from the front coil spring, using a metal clothes hanger or a bungee cord. Do not let the caliper and bracket hang by the hose.
Remove the brake rotor by hand. If the rotor does not come off by hand, gently tap the back of the rotor with a rubber mallet to force it off of the hub. Do not use a metal hammer against the rotor, or you will damage the rotor.
Insert your pry bar against the inward side of the steering knuckle, from the front of the truck. Turn the steering knuckle so that the front of the knuckle faces outward from the wheel well. Remove the castle nut from the outer tie rod stem, using a ratchet and socket. Insert the pry bar between the knuckle and the head of the outer tie rod, and pry the outer tie rod free from the steering knuckle.
Remove the mounting bolt from the wheel speed sensor clip on the front strut, using a ratchet and socket. Disconnect the speed sensor at the electrical connector in the wheel well, using your hands. Remove the wheel hub bearing bolts from the back side of the bearing, with a ratchet and socket. Remove the hub bearing from the steering knuckle by pulling it outward from the knuckle. Strike the bearing with a metal hammer until it falls free from the knuckle, if necessary. Pull the speed sensor wire through the hub mounting hole.
Remove the shim plate that is mounted against the steering knuckle, if the shim plate does not simply fall free of the knuckle with the bearing. Clean the outward facing side of the steering knuckle with a piece of 80 grit sandpaper. Remove any oxidation that or rust that you can see on the face of the knuckle. Apply axle grease or bearing grease to the entire hub face on the knuckle. Install the shim plate back onto the knuckle.
Guide the new wheel speed sensor wire through the hole in the center of the steering knuckle, then tighten the mounting bolt to 13 foot-pounds of torque with a 1/2-inch drive torque wrench and socket. Connect the new sensor wire to the connector in the wheel well of the Trailblazer.
Thoroughly grease the rear face of the new hub bearing. Guide the new hub bearing into position on the front face of the knuckle. Install and tighten the hub bearing bolts to 77 foot-pounds, using a 1/2-inch drive torque wrench and socket.
Install the outer tie rod end stem into the steering knuckle, and gently tap the tie rod into the knuckle until it seats. Tighten the outer tie rod castle nut to 40-foot pounds with the 1/2-inch drive torque wrench and socket.
Install the brake rotor onto the new hub bearing face, aligning the wheel studs with the holes in the rotor. Spin a lug nut onto one of the wheel studs with your fingers to temporarily hold the rotor in place. Install the caliper and bracket assembly over the rotor. Install and tighten the caliper bracket mounting bolts to 87 foot-pounds with a torque wrench and socket. Remove the lug nut from the wheel stud when you have the caliper in place and torqued.
install the front wheel and tire assembly back onto the truck. Tighten the wheel lug nuts snugly with a tire iron. Raise the Trailblazer off of the jack stand, remove the jack stand, then set the vehicle on the ground. Immediately tighten the wheel lug nuts to 100 foot-pounds of torque with the torque wrench and socket.
Turn the ignition key to the off position, and remove the key from your ignition.
