The NVIDIA Web Drivers have to be activated with the boot flag "nvda_drv=1". If your NVRAM is fully functional, this boot flag should be automatically set when installing the drivers. Otherwise you might have to add it to your bootloaders config file.
The following bootloader settings are necessary for full functionality:
Kepler- & Maxwell-Generation: InjectNvidia=False / GraphicsEnabler=No
everything before Kepler: InjectNvidia=True / GraphicsEnabler=Yes