Engine Knocking Noise problems of the 2001 GMC Sierra

I purchased this truck with 13,000. Miles on it , ran great. At 30000. Miles motor started to ping like a lifter wasn't working correctly. Took it back to dealer where I bought it, they said it would not make noise. Took service writer out and started truck, engine made load knocking noise. He stated that GMC said that was normal for that engine and that it starts at 10,000. -19,000. Miles. Been in contact with GMC. They state it won't hurt motor,I don"t no why it wouldn't, metal against metal will wear with time!!!!!!!!they are willing to give a extended warranty to 100,000. Miles !!!! I don"t want it I want my truck fixed under the warranty 3yr/36,000 that I have. If they won't honor that warranty what makes me think they will honor 100,000. Warranty.

Engine knocks when starting cold and when pulling a trailer or under a load. Took truck to dealer and was advised that all the 5. 3 liter engines will eventually do it. Also said that general motors is aware of the problem. I then called general motors and asked them about the problem. They said that it was a carbon build up. So they had the dealer do a decarbonasation which removes the carbon build up. When it was finished, it was worse than it was before they worked on it. I called general motors back and then they told me that the pistons are smaller than normal and that they are slapping around in the cylinder walls causing the knocking noise, and that they are not doing nothing about it because it is not doing any damage to the motor. They offered me an extended warranty on the drive train and I declined it. I paid for a quiet running gas motor, not one that sounds like a diesel. The knocking noise decreases the trade in value, regardless if it is damaging the motor or not. If I wanted a diesel I would have bought one. I have been going round and round with gm and the dealer for almost two years and have got nowhere.

While starting up the vehicle consumer heard a knocking noise coming from the vehicle. Consumer took the vehicle to the dealer for inspection, and mechanic determined that the knocking noise was normal.