I own a 1972 240Z, and the speedometer did not work when I first bought it. I ordered a new pinion gear because the nylon cog was worn out on the first one. Well, after only about 350 miles, this one is worn out too and my speedometer does not work. It just abruptly stopped working one morning. Does anyone know what could be causing it to wear out the cogs so fast, and where to buy one? The one I ordered was from Courtesy Nissan, and it took about 2 months to get it, and was pretty expensive to only work for a few hundred miles. Any help is appreciated.