I have a 1994 E-350 15 passenger van with the 460 motor and I am looking to tow my 16 foot enclosed cargo trailer. It is a tandem axle featherlight and weights about 1700 lbs empty and my loaded weight is about 3000 lbs. Am I safe to tow with overdrive engaged? I tried it recently and the transmission didn't jump in and out of overdrive at all on a pretty flat stretch of road.