Torque converters in the newer trucks have 2 stages: (1) a fluid coupling occurs first when you are starting, accelerating or pulling up a big hill, (2) when you are cruising at a constant speed the lock up portion of the converter is engaged and 100% of each rpm is transferred through the converter, just like a standard clutch. With the TorqLoc toggle switch in the first position the lock up clutch is engaged and 100% of the rpm is transferred, transmission temperatures remain low and engine retarders work at 100%. This position is manual and should only be used manually just like a gear would be selected. Factory convertor (and aftermarket) clutch and drive clutch designs have torque limitations and this function should only be used under light load and light power conditions. A adjustable pressure switch is available to disengage the lock up clutch once a set boost pressure or load has been achieved. The second position converts the application back to stock operation or it can be wired to unloc the convertor. The third position is an AutoLoc position that only maintains a lock up when the stock computer has already established a circuit. This position can be safely selected for retarding or under heavy power and load applications. This position can be selected for every day driving in all situations. The TorqLoc also has an overdrive inverter option to have the transmission start in drive. The lock up can be set to hold on untill 5-10 MPH if you have 2nd gear lock up for slow driving condidtions.