Chevrolet Silverado / GMC Sierra. Service manual — part 2627

Fig. 123: Inspect Gear Teeth For Pittings
Courtesy of GENERAL MOTORS CORP.

16. Inspect the gear teeth for pittings.

Pittings are material fatigue on the flank. The total pitting surface may become so large that
smooth running is considerably impaired or the remaining flank face, still bearing the load,

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Manual Transmission - Tremec 5-Speed (TZ0)

will soon be destroyed by wear.

17. If pittings are present, replace the affected components.

Pitting is caused by the following conditions:

Exceeding the sliding and rolling stresses for the material

Incorrect oil viscosity

Excessive operating temperature

Fig. 124: Inspect Gears For Spalling
Courtesy of GENERAL MOTORS CORP.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Manual Transmission - Tremec 5-Speed (TZ0)

18. Inspect the gears for spalling.

Spalling is extensive triangular pits on the flank, spreading from a zone of gray spots or a
fine line of pits at the root. The depth of the exposed surface is relatively constant
throughout. Further cracks may extend from the pits at an angle. In some cases, the damage
may even progress into the tip zone, causing tip damage.

19. If spalling is present, replace the affected components.

Spalling is caused by the following conditions:

Exceeding the sliding and rolling stresses for the material

Incorrect oil viscosity

Excessive operating temperature

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Manual Transmission - Tremec 5-Speed (TZ0)

Fig. 125: Inspect Gears For Overheating
Courtesy of GENERAL MOTORS CORP.

20. Inspect the gears for overheating.

Grayish to bluish black discoloration of the gear, burnt oil, and reduced hardness is caused
by overheating. Due to the reduction in hardness, there is scored or grooved flank wear in

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Manual Transmission - Tremec 5-Speed (TZ0)