Well, I've got a 1998 S10 with a 4.3 in it. Bought it used with about 70,000 miles on it. It seems to have a tick to it all the time, and I can really hear it if I open my door. It isn't rod knock - I've heard what that sounds like. Not really sure what else it could be. I've taken it to the dealer about three times, and each time they've basically told me that they can't find anything wrong. I'd like to say that it's lifters ticking, but I don't know what that sounds like. Honestly, for all I know, it could be rod knock. It isn't an especially loud ticking, you can barely hear it while it's idling, but the harder I push the truck, the more noticeable it is. I'm going to be taking it to them again, and would like to have at least an idea as to what is wrong with it. Thanks in advance for any suggestions.