Where is the modulator valve for 4 speed automatic transmission on a 1998 Pontiac Gran Prix?

The modulator valve on a 1998 Pontiac Gran Prix's 4-speed automatic transmission isn't a single, easily identifiable component like a solenoid. Instead, it's integrated into the transmission's valve body. You won't find a separate "modulator valve" to replace.

If you're experiencing issues related to what you believe is a faulty modulator valve (like incorrect shift points or slipping), the problem likely lies within the valve body assembly itself. Repair often involves replacing the entire valve body or having it professionally rebuilt. You'll need a transmission specialist to diagnose and repair this kind of problem.