1997 Ford Explorer chains in the back of the motor

We heard a noise in our motor that sounds like a rattle. Our garage told us that this explorer has a motor that was developed by ford and mitsubitsi. This motor has chains in the back. They told us it are the chains that make the noise and that we must aspect a very expensive repair. Can you tell me something about it? What do you think is wrong and what can you tell me about the repair and estimated costs? Maybe you have tips for my garage. I live in Holland so there are not so many garages here who want to repair usa cars. Thanking you in advance, Pieke