I have a 2004 Chevrolet Trailblazer with over 125,000 miles. It still runs great, but recently, I have been noticing a slight problem.

On startup, it cranks normally and sounds great. When I put it in drive, there is a very loud vibration that sounds like it is coming from the front of the engine. When I put the transmission in reverse, neutral, or park, the sound goes away. It only does it in drive. It only does this when the engine is cold.

Once the engine warms up, it either goes away completely or lessens. Usually it goes away altogether.

Can you please tell me what this could be?