its super simple. A cable runs from the back of the speedo through the cab floor to the front left hub. It goes through and is secured by a small "C" clip that is covered by the cap in the centre of the wheel. Sometimes on USA buses they have a drive half way along the cable that is for a service light which you dont need. If you get a replacement cable it will be a full length one and is as simple to fit as it sounds and you can junk the little drive box.
