2013 Chevrolet Express 1500 Cargo Owner Manual - Page 214

9-24 . Driving and Operating If the shift stabilization feature determines that a current vehicle speed cannot be maintained, the transmission does not upshift and instead holds the current gear. In some cases, this could appear to be a delayed shift, however the transmission is operating normally. The transmission uses adaptive shift controls. Adaptive shift controls continually compares key shift parameters to pre-programmed ideal shifts stored in the transmissions computer. The transmission constantly makes adjustments to improve vehicle performance according to how the vehicle is being used, such as with a heavy load or when temperature changes. During this adaptive shift control process, shifting might feel different as the transmission determines the best settings. The shift quality of a new vehicle may not be ideal because the Adaptive Shift Control process may not have determined the best settings for a particular shift or condition. Shift quality will improve with continued driving. When temperatures are very cold, the transmission's gear shifting could be delayed providing more stable shifts until the engine warms up. Shifts could be more noticeable with a cold transmission. This difference in shifting is normal. M (Manual Mode): This position lets drivers select the range of gears appropriate for current driving conditions. If the vehicle has this feature, see "Range Selection Mode" under Manual Mode on page 9‑28. 3 (Third): This position is also used for normal driving. It reduces vehicle speed more than D (Drive) without using the brakes. You might choose 3 (Third) instead of D (Drive) when driving on hilly, winding roads, when towing a trailer, so there is less shifting between gears and when Going about 55 km/h (35 mph) or more, push the accelerator all the way down. By doing this, the vehicle shifts down to the next gear and has more power. D (Drive) can be used when towing a trailer, carrying a heavy load or driving on steep hills. You might want to shift the transmission to a lower gear selection if the transmission shifts too often. Downshifting the transmission in slippery road conditions could result in skidding. See "Skidding" under Loss of Control on page 9‑5. The vehicle has a shift stabilization feature that adjusts the transmission shifting to the current driving conditions in order to reduce rapid upshifts and downshifts. This shift stabilization feature is designed to determine, before making an upshift, if the engine is able to maintain vehicle speed by analyzing things such as vehicle speed, throttle position, and vehicle load.