I'm still getting used to the DMAX, having moved up from a '97 6.5l K2500 and am wondering about a couple of things. The truck as an '02 2500 CC, two months old, with 6200 miles on it. We're running winter fuel here now and I'm using DFA with every tank. I've noticed two things that have me wondering - and both have been present since the truck was new.

First, there's a tap sound from the right side of the engine. When the truck is just started, the exhaust has a pronounced tapping sound - a metal on metal sound - which is very rythmic - about 300 times per minute. This is most noticable at the tailpipe. Once the truck warms up, this tapping becomes much quieter at the tailpipe but I can then hear it through the passenger side front wheel well. The driver side just sounds like a diesel. I also have the Duramax Tick, and this tapping sound is definitely something different. If it was a gasser, I'd think I had a bad lifter. After reading several posts here, I'm wondering if I have a bad injector?

The truck seems to run smoothly with lots of power. No smoking, other than white-blue smoke immediately after a cold start and then only for a minute. The only other thing I've noticed is that under a light acceleration at 40 - 60 mph or so, the engine sounds a little rough - almost like an exhaust leak (my dealer checked for this and said they couldn't find one) - however it doesn't seem to run rough. But, definitely not as smooth a sound as my old 6.5. But, more power and better mileage, so if it's just some new sounds I need to get used to, that's fine.

This sound familiar to anyone else?