ak_cowboy

This sounds incredibly dangerous. jack it up and see if you can get any play with it off the ground with your hands.

GATORB8

Holy crap! I'm reading this right? Your tire will jump 4" off the pavement at highway speeds, I wouldn't drive it until you figure it out.

Is there a noticeable vibration in the cab or steering? There is a driveline vibration TSB from ford that may help diagnose. Maybe this is just a severe development of it. Look for TSBs 08-24-2 and 07-10-9

bugs

I'm not sure if the wheel is coming off the ground but the bed is really moving at least that much.

ford4wd08

tires moving that much and a bed moving is a big difference. your bed will move some reacting to the suspension compressing and going back to normal. i dont know if it will move 4 inches but it will move some. the suspension does this to keep your tires on the ground, it has to flex to perform the best.

bugs

had time to play around with the truck yesterday and decided to open the rear end and check for anything out of the ordinary , found nothing so I closed it up and added new diff fuid with friction modifier and took it out for a test run. well the end results were the bounce was gone any clues as to why? I wouldn't think that the fluid would be that bad with only 39k on it.

jayson_waltz

that should have had nothing to do with your problem imo

MedicDiver

I get bad wheel hop in my 2005 with 5.4L3V 4x4. I have to add friction modifier every 6 months or so to stop it. I think the rear end eats that stuff. First 3 times it was under warranty, ford kept adding it to fix the problem.

JJ1983

I had a truck with wheel hop like that (1986 F150, on the front). I changed out tires and rims to see if that was it. I changed out the tie rods, bearings, shocks...everything EXCEPT the rotor. Low and behold, it was the rotor on the passenger side, the wheel face of it was out of round (as you turned the rotor you could see the flange go up and down). Long story short, could your axle flange be bent? I could happen, most likely not, but there is that chance. Also, like others said...could be an out of round tire, off balnce tire/wheel, or bad shocks. Note my experience though, it wasn't any of that .... lol

JJ1983

Strange, like another poster said, Could be the friction modifier alleviated the problem. good to hear you may have cured the issue.

Wish I woulda read better before I went rambling in the above post about the wheel hop on my truck

nashtruck

For the LS diff to be causing the wheel hop the axle shafts would have to be turning at different speeds...right? That wouldnt seem probable but might be possible.