I've recenly purchased a new 04 4X2 SuperCrew and am experiencing the same rear end 'bounce' and vibration that many others are. It's particularly noticeable on cold mornings when the rear end seems to vibrate excessively. However, the biggest problem is when I tow. I'm pulling a small (4X6) trailer and load of less than 2000 lbs and at approx 60 - 65 mph the vibration gets so bad that I cannot drive any faster. The Ford dealer recently force balanced the 4 tires, but it only marginally improved the situation. He says that sometimes it's in the drive shaft, so they'll be pursuing that next. I'm sceptical that it's in the driveshaft myself based on the feel, but I'm no mechanic. I'm concerned that we're not going to get past this and that is unacceptable. I especially bought the truck for towing, and that's where I'm really having the most trouble. I appreciate any insight anyone out there can provide.

 

Could it be an unbalanced load, giving you a very light tongue weight?

I can't imagine the problem you've described....especially since I just bought an '04 and intend to do a lot of towing too. I sure hope its not a driveshaft problem.....

 

This is a problem to some that seems not to have a definate cause/solution so far.
If you wnat to put some effort to try the following, it might provide some clues without doing any changes to the truck.
Jack the rear up so the wheels safely off the ground so the engine can run the wheel in gear.
Run up the spped to the range you have the vibration and note what the rear does.
If it vibrates in a manner that would be objectional, then remove the wheels, install at least two lug nuts to hold the discs in place and try it again.
If this shows vibration at either test or without the wheel then you have a lead in the direction the problem is in.
It might be the drive shaft , mountings or even some combination.
If you should show the problem this way, you will have made a major advancment in the art of finding the problem.
I used this method to find a severe vibration on a Ranger that neither the dealer or a brake shop could think of.
Problem turned out to be brake drum center was bent one side that would grab the brake shoe twice each revolution.
Good luck to you and hope it's this simple.

 

When I test drove the '04 SCrew that I wound up buying, it had pronounced vibration/shimmy/whatever. Not a smooth ride at all.
Dealer replaced all 4 tires, as well as the drive shaft itself, to get a smooth ride. Now my '04 SCrew is the smoothest ride I have, and that includes my Lincoln!

I tow a 17 foot fishing boat...prolly 3,000 pounds total gross weight for boat, motor, trailer, gear. Smooth as silk, at least up to 80 mph. I have not gone faster than that yet.

Stick with it, and work with your dealer. I'll bet the problem is in the D/S. Mine was.

Happy trails,
CW