I have a 2004 Ford F-150 4x4 5.4 V8 SuperCab. Back in February I lifted my truck with 2.5in coil spacer adapters, out back add a leafs 2-3in. Now I can't say for sure it stated then, but for a while now I have an intermittent freeway vibration. Typically around 70-75mph it is at it peak when it does it. Other times it can be very smooth. The vibration is like an oscillation that you can feel in the body. Not much felt in the steering wheel. The vibration can start and stop any time and last for any amount of time, there is no common point for when it starts and stops. Right or left turns does not cause it to start or stop, sometimes it feels like big bumps will start or stop it but not all the time.
I have a rearview aftermarket camera, I took it off and mounted it several locations to view tires. The fronts are steady while at freeway speed and with the vibration.
After tie rods were changed and no play in any suspension/steering parts, the truck has been aligned several times. Tires are new and have been balanced twice. The driveshaft is new (new U-Joints, shaft and slip yoke) and is balanced, which it did improve the vibration but not perfect. The rear brakes have been inspected, no sign of overheating on the drum or the shoes. The lever is all the way back. So I don't believe it is it, although I did not fully disconnect the cabling. If it was the brakes why would it be intermittent. I had a shop replace all bearings in the rear axle, due to the pinon bearing noise. I saw the TSB's already on vibrations and none conform to my situation. The hubs have been checked, with the engine on they are unlocked.
So as I stated I can't say for sure it started after the lift but maybe due to the lift the differential pinion angle to driveshaft and to the transfer case is too high. Maybe I need some pinion shims. But I haven't heard of anyone else needed to do this after a 2-3in lift.
Any ideas? I'm getting tired of chasing this vibration.
IMHO...u-joints or slightly excessive slip joint extension
Thanks but the entire driveshaft including U-Joints are new only a month and half old as well as the slip yoke/joint. Still shinny and sturdy, trust me I checked and rechecked those, no play at all in all directions.
The fact that it's in the body rules out anything in the front from causing vibration. I would suspect driveline first. Is the slip yoke spline greased or dry? If dry that could be a cause. Does the slip yoke slide onto the spline as far as without the lift? If not, that could be a cause. You can try rotating the drive shaft 180 degrees on the pinion flange to see if that helps or not. Do you have a midship bearing? If so that could be going bad. Just some things to consider. If you have a 2.5 inch lift and are using the stock driveshaft I would suspect the slip yoke isn't on the spline far enough.