In cab reverse wire
 

Installing a backup camera and I need to find a sense wire for the camera. Is there any place in the cab to splice in to or do I have to just run a wire back to the tail lights?

No, nothing in the cab

Closest would be on the transmissions Reverse switch OUT wire to reverse light bulbs at rear of truck

Ford used a Black/pink striped wire for years as the 12volt OUT to Reverse light bulbs

Easier to find at the rear of the truck, and since you will be back there installing the camera............................that might be the best place to tap that wire

I just installed a reverse camera as part of the new Kenwood Double Din touchScreen. As @RonD suggests, your best (& simplest) option is to tap into the wire right at your reverse light. It’s a lot easier than fishing for the right wire by your tranny - it removes any guess work/trial & error. Which of course saves you time. You already have to run a wire from the camera into your cab, so bundle 2 wires together and run them at the same time. Then you’ll have your video signal (to your deck/screen) and have your wire that tells your deck/screen that you are in reverse.
That is how I wired the deck in my Ranger, the deck in my fiancé’s Focus, and the screen in my father’s Ram. They all work exactly as they should and caused no problems with the reverse lights.

Yup. The hardest part for me was getting the wire into the cab. Tranny or taillight is easy at that point. Took 5 mins to tap the tail light. Zip tie right along the trucks wiring harness up into engine bay. That's the easiest part. Then for those with an automatic transmission I've heard there is a rubber grommet there that they can poke through. I have the manual so I needed to poke through another wiring harness grommet. Problem with my setup was the wire going to the back wasn't just a wire. It had a plug connector on it. Usually punching through those rubber grommets you want to just make a tiny hole with an awl or something so its tight enough and seals on that wire. I actually had to drill a 1/4 hole through it so I could jam that connector through.

I used one of the floor pan grommets in the back of the cab, there wasn't anyway I was going to be able to jam an RCA cable through where I have other wires going through the firewall. I just put some silicone sealant on the hole for a complete seal.