Where is the Transmission control module located? for 1999 lincoln town car

Hello, this vehicle does not have a transmission control module. All transmission functions that require inputs of sensors are driven through the powertrain control module (PCM). And no, the PCM is not causing the problem. The best thing you can do at this point is hook up a Ford IDS diagnostic tool (or high quality equivalent) and monitor transmission operation from there. You should be able to monitor shift solenoid operation as well as transmission range sensor position, vehicle speed sensor information, and other data that the transmission uses to select the proper gear. A first gear slip is not so common, and I am wondering if you are maybe experiencing some other impedance in the transmission operation or performance of the powertrain. Again, your PCM is not the problem here, and there is no transmission control module. Further, don't take more advice from this person who said the transmission control module is at fault. That party is clueless about this vehicle's transmission operation, 100%.