I think the chain in my np203 has stretched. It has a part time kit. When in 4wd and I put a load on it I get a 'bang' from underneath the vehicle every few rev's of the tires. I don't know when I'll get around to changing it, but would like to have a replacement on hand for when a block of free time pops up. I know there are two different chains, I think the difference is in the width and 'pitch'? There's 1/2" and 3/8" pitch. . Anyhow, how do I tell which one I have, do I need to pull the front output? What's the easiest way to find out, so that I can have the right chain on hand when the time comes?