On GM 700R4 / 4L60E / 2004R trans you have a Throttle Valve (TV) cable hookup. It looks amazingly like a shift cable.
This throttle valve (TV) cable tells the transmission how much throttle you're giving the motor, so it can alter shift points, up and down, and alters internal line pressures. It takes the place of the older external vacuum modulator.
Ideally you need to get a cable that was designed for your 770R4/4L60E/2004R trans. It is noteworthy to say that TH350 and TH200 cables are similar but not compatible. And since the variety of cable applications out there is a long list of lengths available, do some research and make sure it fits your needs. There are some universal ones out there if you need them.
There are also a variety of sources for the brackets needed to mount this TV cable correctly. Most GM TPI/TP applications can be acquired locally or online. Happy Hunting!
Use whatever source you chose for the bracket but pay attention to the adjustment procedures. Follow them closely. If after doing the install and adjustment on your test drive, or other time for that matter, you encounter soft or erratic shifting STOP!!! Your install/adjustment is WRONG! Readjust the cable or installation. Continued driving will kill your trans in short order.