Need help, bad vibration

[powerstrokepribble]

Ok guys I have a problem, I have this vibration on my truck and I thought it was u joints so I replaced them all and the carrier bearing. But it still is happening, so what is it? It only seems to happen when it is not under load like what I call " free spin" but I can't figure it out, please help

[Miskeeter]

I have a similar problem. It is happening while driving in the neighborhood of 45mph. It seems like it's more pronounced in the back end. I have balanced the tires 4 times, rebuilt the front end, replaced the transmission, and two wheels. I have the Nitto Terra Grapplers 285/70/16's. It is driving me crazy. I bought 500 lbs of sand to put in the bed to see if it calms it down but it only changes the speed at which it vibrates. As soon as i get over 49mph its gone. I can feel it all speeds but its the worst at 45 and 75-80mph. It sucks so bad. Money is tight so i can't go pulling things just to narrow it down. Any help would be great!

[acebir]

I have had a vibration or shaking going on in the rear of my truck. I lifted the truck and notice it when the larger tires were installed. I removed the lift back to stock and know I am know running 285/65/20 on my factory wheels. The shaking is back. I was watching the left rear tire spinning in the mirror and noticed the tire looks like it is whobbiling. The movement I am talking about is in and out not front to back.
I got home jacked the truck up put it into drive and was watching the back left tire whobble. I removed the left tire and installed the spare. The whobble is still there but was harder to detect. I then removed the right rear tire and installed the right tire on the left side. I could see the whobble again. I did all this in the driveway with the truck on jack stands. The tires are brand new.
Know heres my questions. Can the rear hub be out of round? Could the bearings in that hub be shot? I do not want to just start replacing parts. I need to know how determine what exactly is wrong.

[Cowboydave24]

i had the same issue at 90km/h , swapped my rear brake pads out and rear shocks and its not there anymore, try that