I have a 04 cdt, 220k or so, auto 4x4. recently I noticed if I sit in heavy traffic &/or I climb steep hills, my temp goes way up. yes, my coolant is clean, no, there is no physical boil over. if I turn heater up to high fan & heat it seems to go away. Yes, my clutch fan seems ok, (took it to a shop, just about fan).engine runs fine. I do have a code about the trans pump giving low pressure, and at times, my trans seems to want to go into 2nd gear when pulling out. I was told it was shift solenoid 2 yrs ago. no one wanted to change them only, they all wanted to rebuild trans. it 2nd gear issue only happens sporadically, for the past 2 yrs. I changed t-sat, pressure washed btwn the rad, condenser, I-cooler & trans cooler, lots of bugs. I haven't yet flushed anything out, like any of the coolers etc. don't know what to use.. I was at a trans shop, told him all this, he said I need a trans rebuild.i changed trans fluid recently, & found tons of small metal flakes stuck to magnet, & what looked like 2 pcs of a snap ring maybe, in the pan. I want to know what u guys think. I don't know if trans was ever rebuilt by previous owners. what brand trans cooler does anyone recommend?
I probably should get a new clutch fan. truck is stock, no lift, no tuner no nothing.

 

Rebuild do it now before hard parts are ruined!

 

i would not drive that truck until the tranny gets fix. rebuild the tranny and you dont feel comfortable or cant do it, take it to reputable shop that knows those trannys. you could have a bad t stat. take it out and see if the truck still gets warm. there could also be an issue with your water pump. you coolant may be clean, but it still could be old and bad,