Which statement about MPRV is correct?

Which statement about MPRV is correct?

• A. Technician A says MPRV modifies main pressure to produce modulator pressure
• B. Technician B says MPRV pressure is used to influence shift points and shift harshness or abruptness
• C. Both Technician A and Technician B
• D. Neither Technician A nor Technician B

Answer: (D)

MPRV’s job is to protect and regulate the main hydraulic circuit, not to create modulator pressure or set shift timing. It acts as a relief device that caps the pressure in the system to prevent damage, rather than generating the pressure that drives the modulator or directly determining when shifts occur. Shift points and shift feel come from other systems: governor pressure and throttle valve position (and, in electronic systems, PCM control of line pressure and clutch timing). Modulator pressure, which affects shift harshness and how the transmission feels during a shift, is produced by a separate modulator circuit, not by the MPRV. So, the statement that MPRV modifies main pressure to produce modulator pressure isn’t accurate, and the claim that MPRV pressure is used to influence shift points and harshness also isn’t correct. Neither statement is correct.

MPRV’s job is to protect and regulate the main hydraulic circuit, not to create modulator pressure or set shift timing. It acts as a relief device that caps the pressure in the system to prevent damage, rather than generating the pressure that drives the modulator or directly determining when shifts occur.

Shift points and shift feel come from other systems: governor pressure and throttle valve position (and, in electronic systems, PCM control of line pressure and clutch timing). Modulator pressure, which affects shift harshness and how the transmission feels during a shift, is produced by a separate modulator circuit, not by the MPRV.

So, the statement that MPRV modifies main pressure to produce modulator pressure isn’t accurate, and the claim that MPRV pressure is used to influence shift points and harshness also isn’t correct. Neither statement is correct.