Shifting issues

[ILY3000]

My wife has a 2021 Chevy Trailblazer RS (15k miles on her) and its got this issue that only shows up during winter. Happened just last winter too. On really cold mornings (like 2-20°F), it wont shift into overdrive for the first 5-7 miles on the highway. I usually warm it up for about 15 minutes, and we live right by the on-ramp, so it hits 70 mph quickly, but it stays at 4k rpm until it finally shifts. After that, and for the rest of the day, it drives totally fine. Is it normal for the computer to hold off on shifting until the transmission warms up?? Never had a car do this before, just trying to figure it out before winter hits again.

 

[b1lly h1tchcock]

No problem with it, I think that's just the transmission staying in lower gears until the fluid warms up. Based on what I heard, newer cars are programmed that way to protect the internals in low temperatures. Also... winter is still far ahead.

 

[PWilson_]

My wife has a 2021 Chevy Trailblazer RS (15k miles on her) and its got this issue that only shows up during winter. Happened just last winter too. On really cold mornings (like 2-20°F), it wont shift into overdrive for the first 5-7 miles on the highway. I usually warm it up for about 15 minutes, and we live right by the on-ramp, so it hits 70 mph quickly, but it stays at 4k rpm until it finally shifts. After that, and for the rest of the day, it drives totally fine. Is it normal for the computer to hold off on shifting until the transmission warms up?? Never had a car do this before, just trying to figure it out before winter hits again.

I'm with @b1lly h1tchcock. That's actually a normal function designed to protect the transmission. The car's computer intentionally delays the shift into the highest gear until the transmission fluid reaches a certain operating temperature. Thicker, cold fluid doesn't lubricate as well, so forcing a shift into a high gear under load could cause unnecessary wear. Warming it up for 15 minutes is good, but the real key is the transmission fluid temperature, which won't climb as quickly as the engine coolant. Once the fluid warms up from driving, it will shift normally. It's a bit jarring to hear the RPMs so high, but it's a feature, not a bug!

 

[ILY3000]

No problem with it, I think that's just the transmission staying in lower gears until the fluid warms up. Based on what I heard, newer cars are programmed that way to protect the internals in low temperatures. Also... winter is still far ahead.

Yup! Just trying to be ready. So its all normal?

I'm with @b1lly h1tchcock. That's actually a normal function designed to protect the transmission. The car's computer intentionally delays the shift into the highest gear until the transmission fluid reaches a certain operating temperature. Thicker, cold fluid doesn't lubricate as well, so forcing a shift into a high gear under load could cause unnecessary wear. Warming it up for 15 minutes is good, but the real key is the transmission fluid temperature, which won't climb as quickly as the engine coolant. Once the fluid warms up from driving, it will shift normally. It's a bit jarring to hear the RPMs so high, but it's a feature, not a bug!

Thanks for the explanation, that actually makes a lot of sense. I didnt realize the trans fluid warmed up so much slower than the coolant. Is there any way to monitor the transmission fluid temperature directly, maybe through a scan tool or app? Just curious if there's a way to confirm its behaving as expected.