I have 2004 Screw 4x4 5.4. This past weekend I was at the lake, towing about 5000lbs boat down to the launch ramp and noticed, that anytime I would have to make a turn going up hill, I would get a harmonic vibration. It almost felt like I was stressing the rearend or driveline. I noticed it in both directions, but when I straightend out, it would go away. Also after unhooking the boat the truck was smooth again. It is not the trailer as when towed behind other trucks there is no vibration. Does anyone know what would cause this?

 

 

Thank You for the response. Not sure what a friction modifier is, but I would try it.

 

It's an additive for your rear end fluid that allows the clutches to slide against eachother with less friction when your rear wheels are spinning at different speeds like during a turn. Just pour it into the oil and you're set!

 

Change rear gear oil.. and add motocraft friction modifier... Good to go

 

I did look up the other threads about this and it is all good information. I am going to change the oil and add the friction modifier. What a relief to find out it is a relatively easy fix, so it really does ease the mind, Thanks guys.

 

 

It has been some time, but I wanted to respond to this post. I was going to changes the fluid in the rearend, but while reading the manual it said that this was not nessesary. It says that this is a synthetic fluid that does not need to be changed for the life of the rearend. So I just bought the friction modifier and installed. My problem disappeared. Thanks for all your guys help.