Rattling noise goes away with A/C off or when clutch is pushed in?

My first instinct was that it was a loading problem on the engine that caused the noise to be much more amplified. It went away when the engine idled a little higher, the clutch pedal was depressed, or the A/C was turned off. It started after I had to get the clutch repaired and subsequently got another transmission installed. Bad troubleshooting on their part. It's exactly the same noise. The truck also got towed 3 times during this time period. Don't know if something got damaged?