V8 Engine Vibration Condition at 1,200 RPM

Some 2019-2020 Silverado 1500 and Sierra 1500 models equipped with the 5.3L or 6.2L V8 engine (RPOs L82, L84, L87) may have a vibration or drone sound around 40 mph (64 km/h) and 1,200 rpm under a light load. Around 1,200 rpm when Dynamic Fuel Management/Active Fuel Management (DFM/AFM) is operating, the condition may seem to get worse after the engine has reached operating temperature.

If the vehicle was maintaining speed, engine speed and engine load while in DFM/AFM mode, the tone of the vibration can shift noticeably and amplitude may decrease slightly as different cylinders are deactivated.

A review of the CH-51450 PicoScope automotive oscilloscope files recorded during the condition may indicate:

  • When vibration was first occurring, there may be a large spike that aligned with E1 (Fig. 6, #1) and E2. (Fig. 6, #2)
  • After the tone shift, the vibration is no longer directly aligned with E1 (Fig. 7, #3) and E2. (Fig. 7, #4)

 

Fig. 6

 

Fig. 7

 

If this vibration is found, remove and inspect the transmission mount for any debris. (Fig. 8) Clean the mount, reinstall, and evaluate the vibration condition.

 

Fig. 8

 

– Thanks to Richard Renshaw

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