Workshop Repair and Service Manuals GMC SIERRA
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00-05-22-002N Disc Brake Warranty Service and Procedures - (May 31 2013) Disc Brakes - part 8

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Once bent, the lathe will most likely not cut properly until the tool holderplate is replaced. In order to verify the condition of the tool holder plate on amachinethat will not cut right, remove the mounting bolt and remove the cutting head fromthe slide plate. With the cutting head titled at an angle, lay the long edge of thetool holder plate down on the flat part of the slide plate. If any gap can be seenbetween the edge and the slide plate, the tool holder plate is bent and the sourceof vibration. Also check to ensure that the cutting arms are lying flat on the upperside of the tool holder plate.If the mounting arm post is bent, it will show itself by having the back of the cuttingarm lifting off the surface of the tool holder.

Gib Adjustment / Loose Gib

As wear occurs between the slide plate and the box it rides on, you must take up theslack. You do this by way of a moveable wedge, which we call the gib. Your lathe manualdetails adjustment process, which you should perform when required after monthly checksor whenever surface finish is inconsistent.

BRAKE PULSATION

Brake pulsation is caused by brake rotor thickness variation. Brake rotor thicknessvariation causes the piston in the brake caliper, when applied, to “pump” in and outof the caliper housing. The “pumping” effect is transmitted hydraulically to the brakepedal. Brake pulsation concerns may result from two basic conditions:

Thickness Variation Pulsation is Caused by Lateral Run Out (LRO). LRO on a brake cornerassembly is virtually undetectable unless measured (with a dial indicator after the brake service) and will not be detected as brakepulsation during an after brake service test drive. If the brake corner is assembled with excessive LRO (greater than 0.050-mm (0.002-in),thickness variation will developon the brake rotor over time and miles. Excessive LRO will cause the brake pads towear the brake rotors unevenly, which causes rotor thickness variation. Pulsationthat is the result of excessive Lateral Run Out usually develops in 4,800-16,000-km(3,000-10,000-mi). The more excessive the LRO, the faster the pulsation will develop. LRO can also be induced when uneven torque is applied to wheel nuts(lug nuts). Improper wheel tightening after tire rotation, spare tire usage, brakeinspection, etc. can be the cause of brake pulsation. Again, it usually takes 4,800-16,000-km(3,000-10,000-mi) AFTER the service event for the condition to develop. The customerdoes not usually make the connection between the service event and the awareness ofthe pulsation. The proper usage of torque wrenches (torque limiting sockets) willgreatlyreduce or eliminate the pulsation conditions after wheel service events. The improperuse of impact wrenches on wheel nuts greatly increases the likelihood of pulsationafter wheel service.

The following are examples of pulsation conditions and reimbursement recommendations:

If the customer noticed the condition between 4,800-16,000-km (3,000-10,000-mi) andit gradually got worse, normally the repair would be covered.
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