I got a chance to tow a 5th wheel triple axle flatbed trailer with a 2007 Duramax / Allison today. The trailer is 4k lbs empty and I had 2k lbs load on it. The truck is quiet and I liked to see the transmission temperature sensor right in the dash, but I expected more pep. Pressing on gas did not cause an immediate acceleration as on my Ram. Could be because of the trailer but it was fairly light... Braking (it has a Tekonsha Prodigy) was adequate, although I could not feel trailer brakes for a while. I noticed that the Duramax cruises at 1.6k RPM at 65-70, unlike my Ram that needs 2k RPM to go 65-70.
Overall, it felt just like a... truck. I did not get the perception that I have so distinctly when driving my Dodge. Proved to myself that I made the right choice in trucks, again.
-P

 

you should be going 75 @ 2000rpm with ur setup.

 

I have an '06 3500 SRW Duramax for work (company truck). The max I tow with it is 125kw generators, maybe 8k worth. I don't have any complaints, do like the Allison and have had no problems with the drive train (41k for miles). But, I too feel alot better when I jump in my 3500 DRW CTD I have not taken the time to look at rpm's at certain speeds. I can also say I would not want to work on the Duramax , love the Cummins

 

New Allison's have a double overdrive in them. Thats why the revs are so low.

 

That could be, since I have not recalibrated the speedo for larger tires. You are right, judging by the fact that at 2000 rpm nobody is usually passing me on the interstate.
-P