As you can see on the pic, I don't have a parameter on my transformation constraint. in the video I follow the guy has an extra parameter called "mapping" which I don't have. I'm wondering if Blender removed this and replaced it with something else?
-I'm trying to get the wheels rotating when I move the main body bone in the animation timeline.
Check your axis.
Recently answered this question re bone drivers.
In the armature (data) properties viewport display tab, turn on Axes. Or use translate tool and put in LOCAL transform orientation mode. Your screenshot is in GLOBAL. This will show the directions of the local axes. For bones Y is head to tail.
Bone on right is root bone, when moved locally in X, rotates other bone in Z.
Mapped from Local X location (0, 1) to Local Z rotation (0, 360), with Z source targeting X
Your axis alignment may differ, can only tell Y from screenshot. Change to suit, but have feeling your wheels will spin if you move car sideways 8).
Note, if you know the diameter of your wheel (d), move pi x d for every rev. to make rotation look real. Generally for wheels would spin a bone on its Y axis, but it's arbitrary.
PS. Whoops, May have got my mapping spinning wrong way, (negate a value in to or from) but you get the gist.)
mapping is the combination of "map from" and "map to" - thats all
