Crazy4x4

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.:-roll

Crazy4x4

Any one? Any one with a 2.5in lift get the same problem.

effects4

I have a 2" leveling kit on the front of my FX4 and have never had a vibration. I did get a weird vibration once, started out really faint and got progressively worse. Turned out it was a failing spark plug.

Crazy4x4

Thanks, at least I know it is not engine related, when it does it, it does it even with the engine off.

Anyone else have any ideas?

effects4

you're right, plenty of people have lifted their truck 2-3 inches without adjusting the pinion angle. I've never messed with it in a truck but used to change/check it a lot when building race cars.

Can use this as a method to check

http://www.hotrodhotline.com/md/html..._harmonics.php

Crazy4x4

Thanks for the link. I need to get an angle finder now.

F150_Life

My truck is lifted with 35" tires and I experience the same thing except its really only when I'm picking up speed to enter the freeway (55-60 mph) and I feel that rear end vibration. After doing some research I'm learning it's my rear all together. It's a light weight truck and so the bed shakes. I could very well be wrong but it makes sense to me .. hope its nothing serious