Hard, Soft, Delayed or Slipping 1-2-3-4 Shift Document ID: 1593288
GM gave me this printout when I took my car in for transmission service. Thought it might be useful to those that live in colder areas.
6L50 / 6L80 / 6L90
DOCUMENT ID: 1593288
HARSH, SOFT, DELAYED or SLIPPING 1-2-3-4 SHIFT
Note: On cold days, approximately 32°F (0°C) or colder, the transmission is designed to shift differently. The transmission uses a warm-up mode shift schedule until the engine reaches normal operation temperature. While the transmission is in warm-up mode, it is normal for transmission upshifts to be delayed or held longer. This feature improves heater performance by giving quicker vehicle warm-ups.