I recently pruchased a bone stock 08 CC DRW 4wd manual trans, absolutely love it. Here's the problem....my temp gauge has stayed just a hair to the left of dead center straight up while driving since I got it about 2,500 miles ago, runs great no problems. Today I put a 15k tractor on my trailer and headed down the road, pulled it no problem, easily I thought. Then it started pegging the coolant temp gauge out about every 5-10 miles. It would go from normal to pegged instantly and the reduced power would come on. I pulled over checked the fluids and every thing was full and dry. The gauge would go back to normal and few miles down the road it would go from normal to pegged again, instantly. Got rid of the tractor and didn't do it again all the way home. Any ideas? thermostat? I'm new to the 6.4s and was really loving it until tonight.