Towing Grand Marquis

I've owned 9 Grand Marquis LS's since 1988,, putting about 45-50K miles a year on them. Very reliable and perfect tool for my job as a national sales manager. Obviously, I am a fan, but not very confident you would be happy towing with that low rear axle ratio. I towed a 16' flatbed tandem axle trailer a few thousand miles with a loaded weight of 3800# and it did ok with the overdrive off. Load was low on the trailer, well below roof height. When I towed an enclosed, flat front, full height tandem-axle trailer that weighed 3500# loaded, it was like I had tied an anchor to the back of the car. The extra wind resistance really did a number on the 2005 GM, spending much of it's time hunting between 2nd and 3rd gear at 60-65 mph in generally flat terrain. Cruise control was useless, shifting constantly. Engine temp never moved, didn't check trans fluid. I am confident of the weights, because we have scales at the plant. Anyway, love the cars, but you might want to tow that weight and style of trailer before you commit.