2002 might have had the "improved" system. AFAIK, the replacements from Ford of the aftermarket do the trick. If the engine is not making the death rattle on start up, you can wait a while methinks... This here link will get you all the detail you ever wanted on the subject, plus a host of others. It's all Exploders all the time:

correct parts #'s 4.0sohc guides & tensioners with pics... - Ford Explorer Ranger Enthusiasts "Serious Explorations"®

Thanks for the reps btw, good luck with your projects.