Towing with Dodge B1500 Van V-6

I tow a TM 2720 SL with a Dodge B1500 V-6 Van. I pull with only a class III hitch, no WD or sway control. It pulls like a dream, does not move when a 18 wheeler zooms past! I have to keep looking in my rearview mirror to see if it still behind me!
I do have a question though. Is it necessary to have a transmission cooler installed on my van? I had a TM dealer tell me it was not needed since the weight was so light and the height of the trailer was lower the the van (minimal wind resistance).

Appreciate any advice!