Hummer H3. Manual — part 1504

Light scoring is identified as rough, partially porous lines or areas aligned in the direction of
sliding. When the film of lubricant is torn away between the flanks, this permits direct
metal-to-metal contact causing seizure or welding. These welded zones are immediately torn
apart again, producing the damage associated with scoring. Scoring initially occurs in areas
subjected to high hertz frequency stresses and high sliding speeds, usually along the tooth
root and tooth tip. Light scoring only covers a part of the entire surface of the flank or is not
strongly developed and has caused only insignificant wear after smoothing.

18. If light scoring is present, replace the affected parts.

Light scoring is caused by the following conditions:

Inadequate oil viscosity

Unfavorable gear geometry

Temporary lack of lubricant

Surface roughness

Faulty heat treatment of the gears

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

Fig. 152: Severe Scoring On Gear Teeth
Courtesy of GENERAL MOTORS CORP.

19. Inspect the gear teeth for severe scoring.

Severe scoring is the same as light scoring, except large areas of the tooth flank are affected.
At an advanced stage, the flank may heat up to such an extent that localized discoloring
occurs.

20. If severe scoring is present, replace the affected parts.

Severe scoring is caused by the following conditions:

Inadequate oil viscosity

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

Unfavorable gear geometry

Temporary lack of lubricant

Surface roughness

Faulty heat treatment of the gears

Fig. 153: View Of Flank Fatigue On Gears
Courtesy of GENERAL MOTORS CORP.

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3

21. Inspect the gears for flank fatigue, causing gray spots.

Gray spots are localized pittings on the flank caused by material fatigue and extremely fine
pittings formed on the load-bearing flanks. If they are in cluster, they appear to the naked
eye as matte gray staining. Under high magnification, a large number of microscopic cracks
become visible on the flank. Pittings originating from these cracks may create the
appearance of local flank wear. Most of the gray spots are located in the root zone of the
gear teeth.

22. If gray spots are present, replace the affected parts.

Gray spots are caused by the following conditions:

Material fatigue

Contact pressure

Sliding movement

Composite friction

2007 Hummer H3

2007 TRANSMISSION Manual Transmission - Aisin AR5 - H3