Harsh Garage Shift

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Harsh Garage Shift

Checks	Causes
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 operating 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.
Engine	Elevated engine RPM - Verify correct engine operating rpm per application.
A/Trans Fluid Pump Cover Assembly (219)	Inspect for damaged, stuck, sticky pressure regulator valve (233) and springs (234 and 235). Inspect for damaged, stuck, sticky isolator valve (236) and sleeve (237).
Control Solenoid (w/Body and TCM) Valve Assembly (314)	Incorrect or inadequate adapt activity - Perform Reset Transmission Adapts procedure. Incorrect TCM temperature reporting - Monitor TCM temperature using Tech 2. Line pressure control solenoid incorrect pressure.
1-2-3-4 and 3-5-R Clutch Assembly (51)	Inspect for damaged 1-2-3-4 clutch piston (414), piston housing (417), spring (413), and dam assembly (412). Inspect for cut, worn, or damaged 1-2-3-4 clutch piston seal (416), inner seal (423), and housing seals (424 and 425). Inspect for improper selective 1-2-3-4 clutch backing plate retaining ring (429). Inspect for damaged 3-5-R clutch piston (421), apply ring (405), and spring (420). Inspect for cut, worn, or damaged 3-5-R clutch piston dam O-ring seal (418), inner seal (419), and outer seal (422). Inspect for improper selective 3-5-R clutch backing plate retaining ring (400).