What's the mechanism that makes the clicking noise when our tires slip? i know it's the fancy trac control, but why does it sound like a plastic gear? anyone know how it works ? all i can think about are "zipties" when i hear that noise.

The brake pressure modulator valve contains solenoids that are pulsed at a very rapid rate, when slippage is detected. It sits on the engine side of the dash panel, just in front of the driver.

sorry, i think i asked the wrong thing. I meant, "when the wheels are (spinning)". we have ABS brakes, Traction control and rear locker. when the locker kicks in, does it have the same type of electrical solenoid that tells the locker to lock?

Correct me if I'm wrong f5: the traction control and Sabilitrak are both applications of the ABS system to the various corners of the truck to control wheel spin and reduce risk of spinout or rollover. So you're hearing the same sounds that you'd hear when the ABS kicks in during braking.

I can't imagine that the locker has anything to do with trac control and stabilitrak. It's too slow locking and unlocking to be able to help control wheel spin.