Don’t know what the rest of you are building, but I, for one, am SO glad that vex released the various add-on packs with long- and odd-length beams.
Modeling and scaling are so much better now! See attached photos
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very interesting as the dispensation control system, could you send a photo view from the bottom?
Sorry, Valeria~
I no longer have this build. You are the first to express any interest, so I just took it apart without photographing the bottom. 
I can tell you that it WAS able to pull a lot of weight.
There was a single motor with rack and pinion under the hood. Because of the tight tolerances, I had to take the tank treads / fenders off to allow for full range of motion. I hope vex will release new parts for this type of steering and new beams that will make a smooth curve for fenders.
A differential underneath transferred power to the front right and back left sets of rear tires (opposite corners). This sometimes caused the power train to send power to a single set of wheels and caused the bot to spin in place if both sets of wheels were not in good contact with the ground, but if there was a little weight placed on it to keep the wheels down, like a semi trailer, it worked great. (I used this opposite corner drive system design because it is one that real semis use.)
The brain and four motors (!) were all housed in the sleeper cab, but I had to place the battery under the bench seat and between the fuel tanks. I then ran jumper wires to the brain - a creative “cheat” to keep the proportions right. Having the battery this low did give it a low center of gravity for pulling, though.
I think this drive system and low center of gravity design would be a good start for an ATV, too. Of course, I doubt vex would allow the battery to be seperated from the brain for competitions, but for general building, it gives you more options.
Off-road tires with larger tread is another item I hope vex releases soon.
The only other components that were not standard vex were the two blue straws used for the exhaust stacks.
This is a really old post, Valeria. Thanks for looking at it and for asking about it!
~Vexatron