We have a 2005 3500 drw with the 48re trans. only 60,000 mi. on it. Fluid change every 30,000,atf4 and filter .The towing I do is pull a two axel trailor once in a while with my 3500 lb tractor.The truck has been used to carry a 2500 lb slide in camper for about 20,000 mi.The trans has recently devloped a 1-2 shift hunt at low speed,not a major problem I just speed up a little and it goes away.After much research on the forums and asking my friend who is service mgr at the local dodge dealer I found it is ususlly a problem with something called a governer speed valve solonid.Very easy repair with pan off at fluid change.I picked one up at the local cummins repair shop for 61 dollars and will change it out next fluid change.I will let you know if this fixes the problem.
ramp