I have a 94 Z71, 5,7L, auto with od, and a 3" body lift. Occasionally when you start from a dead stop the truck sounds like the fan is hitting the shroud. Example: from a dead stop on an incline when under a load or pulling a heavy trailer there is a loud machine gun sound coming from under the hood. I have already replaced the motor mounts and it didn't seem to help. You can put the truck in gear fwd and reverse and hold the brake pressing the gas and I can't replicate the noise and the engine sits in place. Since it only happens when the truck is moving it is difficult to see exactly what is hitting what. Any ideas are appreciated.