To access it, you'll need to remove the transmission from the vehicle. This is a significant job requiring mechanical expertise, specialized tools, and likely a transmission jack. There isn't a single location; the exact position of the solenoid(s) varies slightly depending on the specific transmission (e.g., 4L60E, 700R4) your truck uses. You'll need to consult a repair manual specific to your truck's transmission to locate the correct solenoid(s).
In short: You won't find it easily without significant disassembly of the transmission. It's advisable to seek professional help from a transmission specialist or mechanic for any solenoid-related repairs on your transmission.
