Finally took the time to drive the new 6.7. Started and it was missing! The sales man didn't act like anything was wrong. I stoped after about 2 min. of idle time. Makes a person wonder! That was the only one I drove so I don't have a comparison.

 

I also test drove a 6.7 with the 68RFE trans; it wasn't missing, just smooth. I was surprised to see 1800 rpm at 73mph - that should be pretty nice on fuel mileage after it gets broken-in. Waiting to see if my youngest son will get his loan to buy my current one.

 

Yeap, I drove one also and I heard what you did. It took a minute to figure it out. It was the exhaust brake engaging to help warm up the engine. I hit the exhaust brake switch ( center dash switch under radio) and the funny sound went away. This is probably what you heard. It's a fluttering sound.

 

I know what your talking about the ebrake but that wasn't what it was. It was very easy to feel not just hear.

 

Try test driving a different one since that one was obviously a bit off. The one I drove was smooth as silk. It was an '07 3500 dually 4x4 with the 6.7 and 68RFE, with a ton of extras...sticker was 51+ and I got them down to 41,500. I will probably end up buying it if my son's loan to buy mine comes through. If not, them I may wait until the '08's come out and look for a srw 3500.

 

My truck upon a cold start will seem like its missing, but it goes away with in 30 seconds of driving, its not the exhaust brake either.. I haven't thought much of it... it runs a hell of alot better upon cold start than my 1999, so therefore i really don't care. lol!