[duramax4sure]

For the first 50K miles my duramax showed 1800 rpm's at 60 mph. Now I have intermittent problem where the engine will show 2000 rpm's at 60 mph. If I stop turn off engine for few secs and then go 60 it will be back to 1800 rpm's. Any suggestions on why this is happening?:muahaha:

 

[modified]

The torque converter unlocking will increase the RPM's about 200.
Do you live in a cold climate?
In cold winter, my torque converter doesn't lock until about five miles down the road. The Allison prevents Lock Up with sump temp below 86 Deg F. Also read about Heater Performance Mode below:
http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3931EN.pdf

You may want to move this post to Allison OEM.

 

[crewzindmax]

that makes the most sense, but with what you said about shutting it off then back on after a few seconds, it could be your speedo on the way out the door.

 

[duramax4sure]

intermittent RPM'S

Im in Yuma AZ, so don't believe its to cold outside. This problem is recurring more often. When I start out in Morning it usually will occur and will remain 2000 rpms at 60 for ever. Like over 30 miles. After getting to town and stopping for a hour or so it usually will be alright like 1800 at 60. But, not always. The Chev Dealer here says no codes will show because the check engine light is not lite. I'll try your suggestion of going to Allison.

 

[modified]

A good test here from DURAtotheMAX, to verify if torque converter is locked or not.
See post #8-13.
http://dieselplace.com/forum/showthread.php?t=60397