What's the situation when an automatic transmission doesn't shift at 3500 RPM?

[RubyFitz]

Here is the relevant introduction about automatic transmissions: Meaning: The so-called automatic transmission means that there is no need to manually shift gears while driving. The control system of the automatic transmission automatically selects the appropriate gear based on the engine's RPM and load, replacing the driver's subjective judgment of timing and shifting operations. Advantages: The advantage of automatic transmissions over manual transmissions is that they are easier to drive. Additionally, automatic transmissions include continuously variable transmissions (CVT), electronic paddle shifters, and electronic gear lever shifting.

[DelLucy]

I had a similar experience last time I drove an automatic transmission car—the RPM soared to 3500 without shifting up, which was really frustrating. It happened while climbing a mountain road, and the transmission delayed shifting because it thought I needed more power. Later, I noticed this issue even during normal driving. It could be due to dirty or insufficient transmission fluid, causing low oil pressure and getting stuck in a lower gear. Another possibility is a clogged shift solenoid valve, which is inside the transmission and controls the oil flow. A common issue could also be a faulty vehicle speed sensor—if the computer doesn’t know the actual speed, it won’t shift up. I recommend first checking the transmission dipstick; the fluid level should be between the cold and hot marks to be normal. If that doesn’t help, it’s best to visit a repair shop to scan for trouble codes.