Are there any changes at all between the two?

 

as far as we can tell, new dash and better tires

 

Also better brakes hand and foot, less vibration due to a rubber mounted exhaust and maybe even electric 2/4wd switch.

 

There are a few changes worth noting, the 04 400 has a 34mm carb with a primer(this is a bigger carb). The front fender flares have been extended out 2" to provide better coverage. Also you get a 2" receiver hitch so you can use your truck stinger on your ATV. The foot brake is hydraulic now instead of cable operated. To top it all off you get the electric shift 4wd switch and a relocated seat release latch.