dirtsavage

I've been running RC cars and trucks for over 15 years. This is the classic sign of a gear stripping inside of the servo. You may still get steering action when the truck is moving. But when the truck is sitting still, the pressure that is exerted on the servo gear will cause it to skip cause of the teeth that are stripped on the gear in the servo. Hence the "clicking" noise. If you think about it, on a real car without power steering, it is hard to steer the car when sitting still. Once the car moves forward of backwards it is easier to turn the wheels. Well the same applies to RC trucks. Plus the larger the size of the tires, the more stress and pressure the servo gears undergo.

You should swap out the steering servo for a high-torque metal gear servo. This will vastly improve and bullet proof your steering set-up.

Hope this helps!
Good Luck!!