No reverse

This is normally a torque converter issue or valve body issue. The fact that it runs well except for reverse, we need to start with the fluid.

Let's service the trans not only to check the condition of the fluid and level but to make sure you don't have metal in the pan or even friction material.

Here is a guide that will show how to do this:

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Next we need to check for codes and make sure there are no codes. I suspect there will be but that will help confirm what the issue is.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Let us know about the fluid and then any codes and we can go from there but I suspect we are going to have to replace the valve body at the least.

At this point we need to drop the pan and inspect for metal and more then likely it needs a pump, torque converter, and valve body.

This is not extremely common but I have seen it enough on this vehicle to know that this is what will be needed.

To confirm this is all that is needed, we need to do what is called an air check. This requires the valve body to be removed and then apply air to the channels and make sure the clutches clunk and that proves the seals are okay.

Thanks