Nothing to worry about. It is just the way the system gets the engine hot faster. This behavior appears somewhere in the manual (sorry.. can't remember exactly and don't have it at hand). As posted later, is the trothle fully open while the engine is cold. It can last from seconds to one minute. I kinda' like the sound

Also, watch the RPM's while driving with the Cruise Control and highway downhills. The system will use the tranny to reduce speed and or keep cold the tranny oil. Anyway, it's a heavy truck so you will get on 70mph easily.

My 2 cents. Enjoy your -D-.

Regards,

 

Dont worry about it all my Dodge trucks and my Durango do it. As fro towing , i tow a 26ft boat and a 4000lb camping trailer over the Smokey Mts with my Durango. No problems.

 

You know, it's interesting -- my '05 Durango 4.7L has the roar that subsides within a minute or so, as has been described here.

But I have not heard the roar at all on my '05 Grand Cherokee 4.7L. And it definitely has a belt-driven fan. Hmmmm.... I've only had it a couple weeks but that roar is just unmistakable and I know I haven't simply missed it.

Maybe since the Jeep is unit-body, they took some measures to prevent that from occurring, perhaps with a different type of coupling on the fan.