General Repair Instructions -680640111

TM 5-2420-224-20-1

Destructive Pitting. This type of pitting occurs after initial pitting, often at an increasing

rate. This will destroy contact area and reduce the gear's ability to carry a load. Rapid

destruction will occur with use.

Abrasive Wear. This damage is caused by the fine particles that may come from many

sources: metal detached from gear teeth or bearings, abrasives not completely removed

before assembly, sand or scale from castings, or other impurities in oil or air.

Scoring. Slight scoring, scuffing, galling, or other surface damage is identified by tears or

scratches in the direction of sliding. It starts in areas having the highest stress and

speed. This is usually at the tip of the teeth.

Burning. Burning is indicated by discoloration and loss of hardness due to excessive

temperature. This is caused by too much friction resulting from overload, overspeed, lack

of backlash, or faulty lubrication. If discoloring can be wiped off with clean cloth, such

discoloring usually can be traced to oilburn-trains, which are not serious.

Rolling. This damage occurs mainly on plastic gears. Rolling is when material is pushed out

of shape without breaking off. This is caused by heavy, even loads; sliding; or overheating.

Brinelling. This can be identified by tiny indentations or ridges on the shoulder or race of

a bearing.

Splines. Inspect shaft splines for wear, pitting, rolling, peening, and fatigue cracks. In many

cases, the same inspection procedure will apply to gears. However, the problem will often be

much less pronounced. Have a magnetic particle inspection performed on splines, if needed.

Tubes, Hoses, Fittings, and Connections. Check all hose surfaces for broken or frayed fabric.

Check for breaks caused by sharp kinks or rubbing against other parts of the truck. Inspect air

tubes for kinks. Inspect the fitting threads for damage. Replace any part found defective.

Following assembly and during initial operation, check for leaking fittings and connections by

coating fittings and connections with soap solution. No leakage is permissible.

Electrical Parts. Inspect all wiring harnesses for chafed or burned insulation. Inspect all terminal

connectors for loose connections and broken parts.

Metal Parts. Visually inspect all castings and weldments for cracks. Parts that carry a great

load should receive magnetic particle inspection. Critical nonferrous parts may be inspected with

fluorescent penetrant.

10.

Brake Rotors. Check surfaces of brake rotors for cracks or badly scored finish and for glossy or

heat spots. Check brake rotors for external or mating surface cracks and for balancing weight.

WARNING

D r i l l i n g and grinding operations are hazardous to the eyes. Eye protection is

required.

Burrs. Remove burrs from gear teeth with a fine-cut file or hand grinder. Remove burrs on

closely fitted mating surfaces by lapping the surfaces with emery cloth.

Exterior Parts. Chassis and exterior painted parts may be resurfaced where paint is damaged,

or where parts have been repaired, by using an abrasive disc driven by a flexible shaft. Paint

metal surfaces as required.

Bearings. Remove residue and oil stain from bearing races with emery cloth.

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