REMOVAL & INSTALLATION
- Remove the brake pads and the caliper, as detailed in the appropriate section.
- Check the disc run-out, as detailed following, at this point. Make a note of the results for use during installation.
- Remove the grease cap from the hub. Remove the cotter pin and the castellated nut.
- Remove the wheel hub with the brake disc attached.
- Perform the disc inspection procedure, as outlined in the following section.
- Coat the hub oil seal lip with multipurpose grease and install the disc/hub assembly.
- Adjust the wheel bearing preload, as detailed following.
- Measure the disc run-out. Check it against the specifications in the "Brake Specifications" chart and against the figures noted during removal.
If the wheel bearing nut is improperly tightened, disc run-out will be affected.
- Install the remainder of the components as outlined in the appropriate sections.
- Bleed the brake system.
- Road test the truck. Check the wheel bearing preload.
See Figure 1
Examine the disc. If it is worn, warped or scored, it must be machined or replaced. Check the thickness of the disc against the specifications given in the "Brake Specifications" chart. If it is below specifications, replace it. Use a micrometer to measure the thickness.
The disc run-out should be measured before the disc is removed and again, after the disc is installed. Use a dial indicator mounted on a stand to determine run-out. If run-out exceeds 0.0059 in. (0.15mm) on 1978-83 models or 0.0028 in. (0.07mm) on 1984-88 models, replace the disc.
Be sure that the wheel bearing nut is properly tightened. If it is not, an inaccurate run-out reading may be obtained. If different run-out readings are obtained with the same disc, between removal and installation, this is probably the cause.
WHEEL BEARING PRELOAD ADJUSTMENT
- With the front hub/disc assembly installed, tighten the castellated nut to the torque.
- Rotate the disc back and forth, two or three times, to allow the bearing to seat properly.
- Loosen the castellated nut until it is only finger tight.
- Tighten the nut firmly, using a box wrench. Make sure the disc rotates smoothly.
- Measure the bearing preload with a spring scale attached to a wheel mounting stud.
- Install the NEW cotter pin.
If the hole does not align with the nut (or cap) holes, tighten the nut slightly until it does.
- Finish installing the dust cap, brake components and wheel.