2000 CRV making thumping noise

We have a CRV that makes a thumping noise after you let off the gas when you accelerate. We took it to a shop today and they put it on the lift and looked at the front end and the mechanic said that the suspension and all looked ok. We are taking it back tomorrow to have the chief mechanic take a look at it. Can anyone give me an idea what is going on so we know what we're getting into? Any help is appreciated. Thank you in advance.