I have a 2008 F250 6.4. It is deleted and has a 6” lift on 37s with 370k miles.

the truck runs great, but at highway speeds(70-80mph) if I take my foot off the pedal and let it coast the truck will have a vibration that feels like a rumble strip for just a second.

I have managed to get the pedal to the exact spot the vibration is happening and hold the vibrations there, but right when I move the pedal back or forward the vibration goes away and the truck drives fine.

I have no idea where this vibration is coming from except that it seems like the rear of the vehicle.

I haven’t found anywhere online with this same issue and I’m lost on where it could be coming from.

any help or ideas is greatly appreciated.

 

If it has a 2 piece driveshaft, check the center bearing and rubber mount.

 

it doesn’t. It’s a supercab with a solid driveshaft

 

A few questions,
Was the vibration a problem before lifting the vehicle ?
Was any work done to the driveline ? May be a phasing problem.