Oil Temp Overheating issue

[garystruck]

Hello,
I am having a Oil temperature overheating issue on my 2008 cm871. Truck is at 450 hp runs good and does not consume oil. Started noticing oil getting too hot. As soon as I start climbing a hill oil temp will go over 245 and climb steadly. the most I have ever let it get to is 248 and then I would pull over and let it cool down. I started climbing hills with the fan on and that helps but it still starts going over 245f fairly quick and I would gear down.
Replaced the Oil thermostat it did not help so then I completely pulled it out thinking it might have been a faulty thermostat. Still having the same problem. I do not want to pull of the oil cooler before I know that the problem is in there. Truck coolant seems to heat up fairly quick but does not overheat. Can a water pump or thermostat cause poor circulation in oil cooler causing the oil too get hot?