After effects does not use GPU rendering. That have been many articles on this. That may change in the future but trying to get the current version utilize your big fancy GPU is never going to work. The only thing a CUDA GPU will do is accelerate Ray-traced rendering. That's a very minor piece of the way video is rendered.
thank you Rick, do you know if there are parameters somewhere in the preferences to use more of the cpu during rendering. In my task manager it appears to be only using 5% of the horsepower thus requiring late nights waiting for renders.
More cores = lower individual per-core efficiency. And no, you cannot tweak anything. Many things in AE simply are not multithreaded (yet) and depending on what effects, features and output formats you use, further limitations apply like clip-based formats requiring linear progression and many CoDecs not being threaded, either. As Rick already said, we seem to be writing such posts every second day, so a forum search will bring up lots of info. Aside from that the simple truth is, that for AE you have the wrong system. 48 cores may be super for 3D rendering in respective applications or other number crunching ´programs, but not AE or any other Adobe app for that matter.
Any tips or thoughts on how my workflow should be if preview is slow? Planning ahead including long preview time comes to mind.
Thanks in advance.