Grind during WOT shifting
 

So lately I've noticed it seem to become increasingly more difficult to shift during WOT pulls, however today during one I went from second to third and it actually grinded, and I don't believe I've ever cringed harder in my life. Is this a sign of the syncros failing or could it be something else? The car only has around 32k miles on it. And yes, my foot was to the floor on the clutch before trying to shift.

Have you changed your gear oil yet?

granny shifting and not double clutching like you should?.......

Could be a sign of a failing CSC.
Could be worn synchros.
Could be old gear lube (see B&W_Evader's comment above).

I suggest changing the gear lube first. It probably needs to be done and, if the synchros are worn, you should see some metal in the drained lube (in older xmissions, we'd look for brass-colored, dust-like pieces; not sure what color it would be nowadays).

Edit: Could be low clutch hydraulic fluid level or bad fluid.

I had the transmission fluid changed around 6 months ago with redline already. I checked the clutch fluid and it's full, but it is slightly darker than the brake fluid next to it (probably because I had the brakes flushed a few months ago, so it has fresh fluid where the clutch doesn't).

There are quite a few threads about CSC failure on this site; it's an all too common problem with manuals. IIRC, dark fluid is a bad sign, especially if there are any solids floating around.

if the master and/or slave cylinders are not leaking, bleed the clutch with premium fluid may help.

cold temperature also makes a difference.

I'll see about getting the clutch fluid flushed next week, supposed to be a fair bit of snow upcoming so holding off until after. I really hope it isn't the syncros, not sure when the powertrain warranty ends (car is a 2014), it's very likely it already has. This is my second 370z and even though I absolutely love it, I will probably end up selling it if I have to end up replacing the transmission, been interested in a used Lexus IS-F lately.

I opened the cap on the clutch fluid reservoir out of curiosity and it is pretty dirty, lots of black looking stuff? laying on the bottom, guess that can't be very good. Note: the clutch still works fine, and there's been no fluid loss.

https://i.imgur.com/DUcVGOG.jpg

that's quite common, especially with 32k miles. try to remove it before bleeding the clutch.

keep it updated