Faults:

I own a 2002 C1500 ext. cab with the 5.3L. I absolutely love the truck. But of course the horrible knock is there, and at 34k, has seemingly gotten worse over there 4 yrs I've had it. My cousin, who works for GM, has told me the most common of the issues; that being what is known as a "piston slap," such that the piston as it moves up and down, it will rattle its way up and down the cylinder wall. This happens because the pistons are made of alumminum, and the engine block itself is cast iron, and the pistons are slightly small in diameter, causing the piston to rock, and as the engine heats up, the piston expands, causing the knock to eventually disappear. I work at a repair shop and looked over the existing TSB's on it relating to the topic, and found another possibility. According to the TSB, an o-ring on the oil pump could possibly be cut or damaged, causing aeration of the oil, thus reducing the amount of effective lubrication. but this TSB really only applies if the knock continues beyond that first 30-45 second stretch. I have noticed that my engine, of course when 1st starting up, has the nothing short of obnoxious knock, but the knock seemingly persists, to a lesser extent, but still noticeable. Is there anything anyone could recommend me trying before I drop the oil pan just to check a stupid o-ring...lol. Cuz Id be pissed if I dropped the pan only to find the o-ring is not damaged.

General Comments:

I love my truck, and plan on keeping it for a long time. Is there any kind of sound proofing anyone would recommend. Also, I want to get carpeted floor mats, any website someone would recommend?

~thanks in advance~