Does anyone know hot to enable force feedback with a Xbox 360 controller ??
Can I get the game to somehow detect it?
I already mapped my buttons using a third party software from Steam called Controller Companion.

You can't, because the Xbox 360 controller doesn't have Force Feedback.
You're thinking about Vibration, which is a completely different feature.

Force Feedback is when the joystick or steering wheel is pushing against you when you drive faster.

Well, vibration is only half the story, as you say - the other half being terrain resistance etc. I own a Logitech G27 wheel myself and I know the difference. I was only hoping for the vibration part tbh. And the x360 controller has vibration.

Doesn't the Xbox One controller have forcefeedback in the triggers? Any way to enable those?

No, they're vibration motors, not force feedback ones.

Unfortunately, you can't enable those without a mod.
Most controllers have 2 vibration motors, a large one (for big, heavy vibrations, like explosions), and a small one.
The Xbox One controller has 2 additional small motors for the triggers (even smaller than the regular small motor, I think).

Most games are designed to make use of the big and small motors, but not the left or right trigger motors.

This is possible to play with 360 controller with force feedback on Windows 10 for Star Wars, just launch this software and say yes until installed.

https://steamcommunity.com/sharedfiles/filedetails/?id=165238623

It'll also enable force feedbacks on all very old games like Tony hawk's pro skater 2 etc.