The part that prevents your steering system from pulling itself to bits is this one
The gear starts to slip relative to the axle if more than a particular amount of torque is generated. That means that if you incorporate it into your steering system and the steering hits its stop, the gear starts slipping. Doublebricks, a Russian LEGO users group organise a competition called the Hard Truck Contest, which involves racing PF trucks and they've got instructions for the chassis on their website.
ralph the gear you are talking about can you tell me the name or part number to look for so i can get one cheers paul