Does changing gear ratios cause a at. transmission to not shift into next gear?

Yes, changing gear ratiOS can cause an automatic transmission to not shift into the next gear if the new ratiOS are not compatible with the transmission's design or control system. This misalignment can lead to incorrect shift points or failure to engage specific gears. Additionally, if the changes are not calibrated properly, it can result in slipping or erratic shifting behavior. Proper adjustments and tuning are essential to ensure the transmission functions correctly with the new gear ratiOS.