Engine has a very loud knocking sound when cold from day one. Dealer and GM says it's normal. It's not normal for a truck that cost 28,000 to make this kind of noise.
Transmisson makes a very loud winning or howling noise when gradually getting up to approximately 30-35 mph Noise starts at about 28 mph and stops at 35/37. The noise reoccurs when slowing down or stopping. When slowing down the noise will start at about 25 mph and sometimes continue right down to zero, but not always. The truck is 39 months old, but has only 34,500 miles on it. Dealer says GM most likely won't handle it and they don't know where to start to find the noise. Any help?
Have the transmission flushed and serviced. My 2000 GMC did the same thing around 37,000mi. After servicing, the problem disappeared. I had no more transmission problems to 67,500mi when I traded the truck in. My 2002 GMC is slipping and moaning at 45,000mi. I plan to have it serviced soon. As for the engine sounds, it is common to hear a few rod knocks during initial start-up in very cold weather, any engine from any manufacturer can have this happen. Be sure your using SAE 5w30 weight oil. Your engine needs this oil due to tighter bearing clearances. If your rod knock persists, try a lighter oil in the cold weather, like 5w20, this will allow the oil to reach engine bearings faster in cold weather. The noises may also be piston slap. The LS1 engine has very finicky pistons. Because of the short piston height, they will exhibit piston slap at low engine speeds, 1000 to 1200rpm, especially in a cold engine. Because aluminum has a greater coefficient of thermal expansion then cast iron, GM gave the LS1 greater piston to cylinder wall clearance. This extra space allows the aluminum piston to expand as it warms up. Once at operating temperature, the clearance is decreased and piston slap diminishes.
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