Torque, MaxSpeed and TurnSpeed are deprecated.
You need to script the wheels to work with HingeConstraints. VehicleSeats don’t work automatically like they used to with wheels with surfacehinges.
There is a tutorial about vehicles and scripting them here: Building a Basic Car
You need to change the Torque in the HingeConstraint Properties.
AngularVelocity will be how the speed is controlled from the script.