Multiple problems

First of all, the noise issue is a very big one. Who is this "dog" supposed to be for ? Special Forces ? Not if it makes a racket. Regular troops ? They march by the hundreds and make enough racket already, so just put a truck behind them to carry their stuff, it won't make much of a difference.

I can imagine a robot for bomb-disposal or landmine detection (just have it run over the target zone), but I don't think troops would like regular visits from an ammo robot that would reveal their position on a continuous basis. I have no experience myself, but I don't think that real-life combat resembles Counter-Strike or BF2142 in any way. I think real troops in a firefight prefer cover and concealment. A racket-making robot dragging ammo around every quarter hour would tear both to shreds, not to mention being a walking target of destruction itself (hey, isn't that an ammo dog ? Give me the rocket launcher and tell me where it stops !).

As for the stealth aspect of things, if it is supposed to go on a mission with Special Forces troops, then it needs to be as silent as possible and a lot more enduring than 2 hours, or even four. Special Forces missions are not the kind you do in two hours, in my opinion. Trekking over a few kilometers of jungle to infiltrate an enemy position with the goal of destroying a satellite dish or fuel tanks is not going to be facilitated by a robodog that needs feeding every two hours. And they're not going to carry it until they need it - they have enough to carry already.

Frankly put, aside from bomb detection and eventually disposal, I fail to see where a robodog is really going to be better than a more conventional transport vehicle.