I've got a 2018 F150, 4 wheel drive, 3.7L V6 with 45k miles. Whenever I'm backing into a spot, I'm hearing a mechanical type noise, maybe a clunk. I only hearing when doing this. No other noticeable noises when driving. Whenever I first go from park or forward to reverse, i don't hear it. Whenever I go back from reverse to forward, I do hear it. Happens when i've got wheels turned or whenever they're straight so i don't think it's tires rubbing. Should also mention that if i back into a spot, whenever I go to pull out after cranking, it wants to lurch forward. This pretty much all just happens while the transmission temp is cold. After driving for a while (like 10 mins or so), I don't notice it really. This lead me to believe maybe it's a transmission issue.

 

I am guessing 2018 uses brake drum for emergency brake as do earlier Ford models.
2018 is pretty new for this to be the issue, but may be the friction material for the shoes has fallen off. If I hadn't seen this for myself I would have never guessed to could be the issue.

 

So you think it’s a brake issue? I’m not savvy in the vehicle department but is there anything i can directly inspect myself without screwing anything up?

 

Chock the front wheels and then jack up both of the rear tires. Release the parking brake and put gear selector into neutral. An assistant would be good to have for the next step. Rotate the tires a few revolutions while listening for a dragging sound. Its normal to hear a slight, but smooth, dragging since the brake pads will likely be rubbing against the rotor. What you are listening for is slap accompanied by a change in the sound and added resistance as the wheel is rotated. After a few revs reverse direction and in general you will hear a similar slap going the other direction but not always.
You might want to take it to a good mechanic or brake shop and ask them to inspect for you. They will likely do the sound/feel test first and if they detect an issue disassemble to confirm.
In my local area (Ocean Sprins MS) Goodyear would likely do this for free or for a minimal charge. I would not go near Midas or Pep Boys for this testing unless you have $800 laying around since they will convince you ("I am surprised you made it this far") need new brakes all the way around even if you don't.
We are just guessing that it is the brake pads at this point.
Put it back in park before you remove the chocks.