First try installing the Cuda Drivers and then checking the box that says enable unsupported GPU in the settings. If that works then you're good to go if you really want to use Ray-traced rendering. If that doesn't work, you can still use Ray-traced rendering, it will just be slow. A better option is to create your text in C4D Lite that comes with AE, assuming you have the right version. Personally, I'd use C4D lite. You will have much better and faster rendering results.
The last option is to just stack up your text layer in Z space using copies one pixel apart. That will work in any version of AE that supports 3D layers.
The GTX 970 will never work with the ray-traced 3D renderer. Nvidia changed the architecture so the Maxwell-class GPUs don't work at all with the Optix version that is depended on.
To use 3D in After Effects, use the integrated Cinema 4D features:
Or, if you want to try out extensions like the Zaxwerks plug-ins or Element 3D, they can be useful for some 3D work.
Sorry about the misdirection to try the GTX 970....