There are variations on the parallelogram steering gearbox, including worm and roller.

Yes, there are indeed variations on the parallelogram steering gearbox. One of these is the worm and roller type. This type of steering gearbox uses a worm gear (a gear in the form of a screw) and a roller that fits into the worm gear. When the steering wheel is turned, the worm gear rotates, moving the roller along its threads and turning the pitman arm, which then moves the steering linkage and turns the wheels. This type of steering gearbox is known for its durability and strength, making it suitable for heavier vehicles.