I have a 84 700r4, I need to know what would happen if I don't hook up the lockup switch. I know there will be extar heat but anything else?
I have a large tranny cooler mounted in front of the radiator, and also goes through in series with the radiator.

 

Gas mileage will suffer on the highway. I dunno what else, if anything.

 

It's mainly used for short trips, 20 miles or less. So gas milage isn't that big a deal to me.

 

You will lose about 3 MPG all around. The converter will lock at steady throttle at low speeds too (35-38mph) so it affects around town driving as well. It's my understanding it's best to leave it as an ECM controlled lockup device. The ECM tells the computer to unlock at a certain amount of throttle movement and load values. So if you step into it ,the converter is unlocked anyway. In a stock ECM under WOT or heavier acceleration maintaining converter lockup is not part of it's program. For pure acceleration it's actually beneficial to have it locked. I believe there is a tech article about how to connect a switch so that you can manually lock it when you under WOT. In the quarter mile it's supposed to be good for a tenth or two when locked. I'd leave it as is you will notice the fuel mileage drop and it won't make an around town performance difference. I had mine disconnected and was not impressed. Contact Pro Built Automatics and talk to the owner (Dana?) about lock ups he is an awesome guy lots of information. My $.05