I have an 05 2500 CTD with 11500 miles on the clock now and I am loving every minute of it. On the highway last night, I was running about 80mph and nailed it to the floor just for the heck of it. I expected the truck to drop out of OD to the next gear but it did not. It started to accelerate alright, but I was expecting it to drop to the next gear and really throw my head back. Is this normal? It will downshift at lower highway speeds but it doesn't seem to do this when I am going faster than 70mph. Any thoughts?

 

Computer programming in the PCM on the 05's is different than the programming from previous year 48RE's and way different than any previous generation before that. I suspect it is normal at that speed, down shifting to 3rd at that speed would have it getting close to the governor RPM's. There would be no use for down shifting at that speed and RPM's. So programming I would suspect is the reason why it will not.

 

Thanks, that makes a lot of sense.

 

yes it is normal It will not downshift until under 64mph. Unless you manually do it. If I need mine to downshift a little quicker say at 65-68mph when I am loosing speed going up a hill I will just quickly bump the tow/haul button off then on again. It will down shift then.