downgrading CUDA driver

I installed the latest CUDA driver (with v9 RC) to try out CUDA 9, but I’m getting minorly different results so I’d like to revert to the old (v8) driver. How do I only uninstall the driver and only reinstall the driver (without modifying my installations of the CUDA toolkit)?

refer to the CUDA install instructions for your OS.
For linux it will depend on whether you used runfile install or package manager install.
For windows it should simply be a matter of installing whichever driver you wish. You will not be able to use CUDA 9RC if you don’t have a CUDA 9RC - capable driver.