I have a 2005 F-250 4X4, 4" lift, 35" tires. I have a rear end vibration that begins at around 55 mph and cycles about every minute or two. Sometimes the vibration is so bad it shakes the seats and you can hear my vioce shuttering as I am screaming "I want to burn this *!#@#%". The vibration will completely go away and everything will be smooth as silk for about 30 seconds then the vibration will slowly come back. As the speed increases the vibration gets worse and the cycle continues. I have replaced the body bushings, U joints, tires, brakes and had the tires rebalanced, and still the vibration continues. Today I pulled the driveshaft to have it balanced and decided to run the truck in drive without the driveshaft connected. As I did the vibration began as I increased the rpms. I am wondering if it is normal for the transmission to shutter and vibrate without any load on the transmission or am I possibly dealing with a transmission problem? Any advice would be appreciated.

 

It was the transmission mount.

Funny thing though, I cound not see the transmission move at all when I was running it.