Which statement about downshifts is correct?

Which statement about downshifts is correct?

• A. Full-throttle downshifts are caused by an increase in modulator pressure as the throttle is pushed
• B. Automatic downshifts occur because of spring pressure and the reduction of governor and modulator pressure
• C. Both statements are correct
• D. Neither statement is correct

Answer: (B)

Downshifts in an automatic transmission come from the way the valve body uses hydraulic pressures and springs to select gears. Two main pressure signals influence shift: governor pressure, which grows with vehicle speed, and modulator pressure, which follows engine load and throttle position (vacuum). Springs provide the restoring force that helps move the shift valve to a lower-gear position when the hydraulic pressures drop. When the car slows or throttle changes reduce the hydraulic pressures, the spring force moves the valve toward a lower gear, causing a downshift. So automatic downshifts occur because governor and modulator pressures decrease and the spring force pushes the valve to the lower gear, not because modulator pressure increases with throttle. The idea that full-throttle downshifts happen due to an increase in modulator pressure isn’t consistent with how these controls balance to produce a downshift.

Downshifts in an automatic transmission come from the way the valve body uses hydraulic pressures and springs to select gears. Two main pressure signals influence shift: governor pressure, which grows with vehicle speed, and modulator pressure, which follows engine load and throttle position (vacuum). Springs provide the restoring force that helps move the shift valve to a lower-gear position when the hydraulic pressures drop. When the car slows or throttle changes reduce the hydraulic pressures, the spring force moves the valve toward a lower gear, causing a downshift. So automatic downshifts occur because governor and modulator pressures decrease and the spring force pushes the valve to the lower gear, not because modulator pressure increases with throttle. The idea that full-throttle downshifts happen due to an increase in modulator pressure isn’t consistent with how these controls balance to produce a downshift.