Ok so I just bought this truck and about two weeks later it developed a very faint knock untill it warmed up past about 100 degrees than the sound would disappear completely. Now about a month later the knock doesn't show up on cold start but about 30 seconds later the knock starts very faint then when temperature reaches about 50 degrees it's gets very loud and sounds like marbles rolling around untill it reaches full temperature than it dies down to a faint ticking sound but never goes away untill engine speed reaches exactly 1000 rpm's but comes back around 2000 rpm's. It sounds like it is coming from the bottom end of the engine. I was thinking a pressure plate maybe? Anyone else had any experience with this? Any insight would be greatly appreciated
Thanks
Jake

 

The 99-newer trucks have a very common issue with the cold start knock that usually goes away in a minute or less. GM is aware of this and they say it will not harm the motor. It is actually piston slap from loose tolerances in the motor builds. As much as I hate the noise I have to say I have personally had them with well over 200,000 miles that are still making the same sound and run great. Using a little Lucas oil additive seems to lessen the sound (substitute a quart for a quart of oil at your next oil change). As far as the marble in a tin can sound that may be bad gas. I notice on my 2001 I will get that sound on occasion especially when towing so I try to use 93 octane when I know I will be pulling something. Bottom line - these motors are great, last a very long time, and in my opinion offer a great power to gas mileage compromise. Good luck - I hope this helps.

 

Thank you sir. But the only thing I am worried about is the knock doesn't go away after it warms up. It quiets down alot but never does go away and when I first start the engine it doesn't start knocking for about 30 seconds. Until it actually gets a little temperature then doesn't quiet down until it reaches full temperature!
Thank you