@barry880 Is this issue still resolved? I'm aware that your original post is nine weeks old, but curious to know how it was resolved. Honestly, while I was reading through all the comments, I noticed that azzazel_99's final recommendations were the same that I would have given:
Try that and see if it helps. Heck take your side panel off and maybe set a fan to blow on your computer and see if the added air movement helps. Could be your vrm getting hot or something maybe? I'd try blowing out the psu and make aute it isnt getting hot
Even when the CPU, PSU or GPU aren't directly overheating, excess heat in the case can cause the VRM or Southbridge to overheat, and thereby reboot your system. The typical causes of rebooting are: (1) power (2) heat, (3) software.
(1) Since the GTX 760 and 970 have near identical power requirements, it's unlikely the cause. (2) Heat could be eliminated by following azzazel_99's suggestion (above). Software, although not the most likely cause in this scenario, could be the culprit. I know that you had already removed the drivers, but did you use DDU to do so? Afterwards, reinstalling a driver version by one previous revision number may have been indicated. (Outlier) Another very real possibility is the DisplayPort cable. I've seen several instances of incompatible DisplayPort cables with the wrong pin configuration causing reboots, strange as that may sound. The only thing that I find perplexing is when you mentioned that you tried the GTX 970 in your buddy's rig and it didn't work. Did you mean the GTX 970 rebooted his or her computer as well, or it didn't? (quote below).
ya i tried it in my buddies pc same specs as mine and it didnt work. i got it off amazon..
Stated solution (below). Your description of the solution was perfect. If this was still a problem, I'd be very curious to see a couple of photos of the inside of your rig, to get an idea of it's airflow.
So i took my psu out and cleaned it real good (it wasnt too bad). and then went in and turned my gpu fans down to normal and ever since ive been gaming for bout 2 hours with no hiccups! maybe the psu was a little dirty im not sure but its working for now. i will keep you guys posted if anything has changed. thanks for all the help!!!