Thanks for the compliments all!
@Shimon: That is a good question. I tested a setup with diffs, but the problem was that I did not find the room around it for the gearing.
It is geared down to supply enough torque to pull the trailer, but the gears i would not have like to be visible or disturb the chassis design.
It is a smooth drive though.
@DLuders: I don't buy my bricks at Chromebricks. A friend of mine owns a chroming company were i can chrome a batch so now and then for a much better price, as larger quantities of chromed bricks are almost unaffordable online. Most of it i use myself, but the remains I sell off in my own webshop: http://www.bricklink.com/store.asp?p=Peterbilt
You can not chrome every existing Lego part. They have to be ABS, and unprinted, and above all they should be able to get mounted on the support racks that go into the electrified liquids during the proces. The chome is very nice, like on real metal, but due to the layer thickness building is also tougher. I would not reccomend building a complete structure with it.