Engine Noise

[fastsuv]

I know this is kinda hard to explain, but here goes:
My truck is making a knocking sound at idle. It doesn't happen until the truck is warmed up. It seems to be coming from the drivers side of the truck. Can get really loud in cab. Seems to go away when revving motor. I also took off the serpentine belt, and the noise got quieter. It is not a lifter or injector knock, I am familiar with that on my engine, but it is a lot deeper of a sound. Any ideas? I am not sure of the symptoms of a bad/spun bearing, or other engine problem. Any help would be great!
Kevin
Pewaukee,WI

 

[Richard Le]

My original motor made the exact same knocking sound. We pulled the motor out and discovered that the front main bearings got grooves in them and the crank journals were toasted. I hope your problem is not as serious.