Your model is not to high poly, and the tri count isn't the problem either, it is just not properly optimized yet. So I am not asking you to remove detail, I am asking you to take a critical look and remove vertices which don't add shape to the model.
Here is some feedback:
Red marked are the vertices you could remove. Some don't add anything others just so little they are not worth it in my opinion. Do keep in mind that I am just basing my feedback on screenshots, sometimes it is hard to tell if a vertex adds shape or not. Just remove those you also think should be removed.
If you save some tri's you could 'recycle' them and use them to make your wheels rounder. The rounder your wheels are the better they will look in game. (Though there of course is an optimum in between looks and performance). Some extra sides to your model's wheels would sure look good.
Good luck,
D.J.