They're pretty much custom made. The axles tend to be the only 'donor' part, predominatly from Tamiya (Japanese RC company) trucks. Chassis are now bein produced in numbers, but until recently there were maybe one or two suppliers in the US, the rest were custom jobs. The controls range from straightforward left/right forwards/reverse to independant steering at each end and seperate throttle controls for each axle This is a more basic one, just independant front/rear steering; http://www.tamiyaclub.com/moviecomment.asp...273&uid=169 More 'traditional' design - central gearbox with driveshafts to axles (a la fulsize 4x4) Pretty much as seperated from reality as you can get, basically two axles held together by a beam. Each end has it's own steering and throttle