In Allison hydraulically controlled transmissions, which statements are correct?

In Allison hydraulically controlled transmissions, which statements are correct?

• A. Shift Relay Valves and Shift Signal Valves Control Clutch Application
• B. Upshifts Are Made by Governor Pressure and Modified by Modulator Pressure
• C. Both Statements Are Correct
• D. Neither Statement Is Correct

Answer: (C)

In Allison hydraulically controlled transmissions, shifting relies on hydraulic signals inside the valve body to decide when and how the clutch packs are engaged or released. The Shift Relay Valves and the Shift Signal Valves are the components that manage how pressure is applied to the clutches during a shift, shaping the sequence and timing of clutch engagement. Upshifts are driven by governor pressure, which increases with vehicle speed, and this is further adjusted by modulator pressure, which responds to engine load or throttle position. The governor provides the baseline shift point as speed rises, while the modulator pressure tunes that point and the shift feel to suit how hard the engine is working, producing smoother, appropriate shifts. So, both statements are correct.

In Allison hydraulically controlled transmissions, shifting relies on hydraulic signals inside the valve body to decide when and how the clutch packs are engaged or released. The Shift Relay Valves and the Shift Signal Valves are the components that manage how pressure is applied to the clutches during a shift, shaping the sequence and timing of clutch engagement.

Upshifts are driven by governor pressure, which increases with vehicle speed, and this is further adjusted by modulator pressure, which responds to engine load or throttle position. The governor provides the baseline shift point as speed rises, while the modulator pressure tunes that point and the shift feel to suit how hard the engine is working, producing smoother, appropriate shifts.

So, both statements are correct.