Overheating?

[kc04]

Ok I had my came home yeterday from working out of town. Turbo did very well. I had some good pulls to make and anything too bad i put it in 4th and it was fiine but on flat ground in 5th egts were 1100 or so truck had power but water temp would climb like crazy! So i made 540 mile trip in 4th at 2600 rpm. It sucked bad. What does this sound like? The fan is comin on but i dont think its engaging. Its got plenty of water and no hg leak. Water pump seems to be working and its got a brand new cummins thermostat. I was pullin my 5er which weighs about 12k. Empty the fan seems to run all the time. Is it commom for hg to leak between cylinders?

 

[kc04]

This has me leanin towards gears. I do have 355s with 6 305s on it and im sure its playin a role in this issue!

 

[Teaspoon]

Have you ever pulled the front end apart and cleaned (with a pressure washer) the charge air cooler, radiator, trans.cooler, and a/c condenser?
If you are on gravel alot or run through fields alot the dust or the seed will pack in the cores and cause things to run hot