Do what they do to cats or puppies so they won't be afraid of the pet taxie. Put food and water in front of the cage. When he eats and drinks comfortably, put the food and water inside the door when he's OK with that, keep putting the food and water into the cage farther in. It's slow but it works and don't slam the door when he's inside or he'll think every time he goes into the cage, he's trapped. Play with him at the door, then close the door gently. Tell him he's a good boy and when he goes outside, put his food into the cage, when you want to have him go in. Feed and water him in his cage after he has been out playing. That will be his reward.