Sounds like a clutch issue - too low of a temp, or failed locked. Definitely seen this on GM trucks.... economy takes a nose dive, find the fan stuck engaged 24x7.

Both the 3.7 clutch and the CRD clutch felt like they had about the same level of stiffness when I hold onto their 36mm nut and turn it with my hand, and they were both much stiffer to turn than I expected...I expected them to feel really loose when I turned them by hand...Does this mean both clutches are failed?