Severe vibration while towing

[RandyH2]

I have previously discussed the always-present vibration in my '11 Explorer, it feels like something is out of balance. This new vibration is much more severe, shaking the entire vehicle like it would shake if you drove over rumble strips on the edge of the highway at about 5-10 mph.

While towing my boat (approximately 4500 pounds, total weight including single axle trailer), if I let off of the accelerator quickly while travelling at 40-45 mph (approximate), the shaking begins and will continue until the brakes are applied or the vehicle coasts down to some lower speed (30 mph?). This is easily reproducible.
I have limited towing experience with the Explorer having made about 6 trips prior to this happening. The shaking had not occurred previously though I can not say that I had done the same lifting-off of the accelerator previously- I may have, I just don't know. The exact same boat/trailer has been towed behind our '01 X5 approximately 40 times on the same routes and I never experienced any vibration/shaking so I doubt it is a problem/related to the trailer.

 

[peterk9]

I have previously discussed the always-present vibration in my '11 Explorer, it feels like something is out of balance. This new vibration is much more severe, shaking the entire vehicle like it would shake if you drove over rumble strips on the edge of the highway at about 5-10 mph.

While towing my boat (approximately 4500 pounds, total weight including single axle trailer), if I let off of the accelerator quickly while travelling at 40-45 mph (approximate), the shaking begins and will continue until the brakes are applied or the vehicle coasts down to some lower speed (30 mph?). This is easily reproducible.
I have limited towing experience with the Explorer having made about 6 trips prior to this happening. The shaking had not occurred previously though I can not say that I had done the same lifting-off of the accelerator previously- I may have, I just don't know. The exact same boat/trailer has been towed behind our '01 X5 approximately 40 times on the same routes and I never experienced any vibration/shaking so I doubt it is a problem/related to the trailer.

That definitely doesn't sound right. There are 2 things that automatically happen when you decelerate. One is the Aggressive Deceleration Fuel Shut-Off (ADFSO) and the other is the Smart Charging Alternator which is a regenerative electrical charging system (kinetic). I don't see either of these causing a shaking like you described. Both these system would be operative whether or not you are towing.
I don't recall reading any other posts regarding a similar problem.

Peter

 

[Jwhcars]

Try a test drive in sand mode. This I think should change distribution ratio of the power to the wheels. I am not sure if it changes the transmission ratios ( I think it does ). If your vibration goes away you now have narrowed it to the area in question.
I would not take the time to hook up the trailer , just drive it.

 

[Dr Plastic]

Did you press the tow mode button?

 

[RandyH2]

Yes, Tow Mode was activated.