I have a 2005 Dodge Ram 2500 Cummins quad cab 2WD 48RE transmission. The RPM spikes from around 1700 to 2800 when I force the shift from OD to 3rd in Tow/Haul mode. This happens when I am pulling around 12,000 lbs or empty. Is this normal? A mechanic friend seems to think this could be damaging to the tranny and drivetrain.
Roy

 

You should be O.K. The only thing to really watch is overrevving the engine. You will drop a valve seat/valve if you do. If you are doing this to slow down, get an exhaust brake, you won't have to be shifting it to stay at speed.

 

The 05's still only had O/D lock-out as Tow/Haul, no? So you're downshifting which raises RPM's.