My 2008 LMM overheats (both engine and tranny) when pulling heavy 5th wheel trailer (15,000#) on grade or into headwind at freeway speeds (65+). Slowing down, or shifting down to 4th or 5th gear, and both temps return to normal fairly quickly.

Otherwise temps are fine.

In a previous DMax (03), overheat would activate fan (loud), and temps would return to normal.

In this truck I don't hear the fan cut in.

Does the LMM have a fan clutch which should cut in with rising heat?