I have a 1988 F150 single cab 4X4 6cyl manual transmission stock height truck. I have a vibration in the drivetrain at about 60mph.

I have removed the rear driveshaft, locked in the huds and put it in 4hi. Took it down the highway at 60mph+ and the vibration is gone.

I took the rear driveshaft down to a driveshaft shop and they said it looked fine. Has not been cut on, no dings or dents.

My rear yoke that is coming out behind of the transfer case and into the front joint of the rear drive shaft has some dings and nicks in it. I think that may be causing my vibration.

I cannot find a place online that has one for sale to save my life. Do you know where I could find one besides a salvage yard?

 

check the u joints. that happened to me with my truck. at higher speeds, it would make this vibration and a humming sound. it turned out it was u joint in the rear driveshaft.

 

I just put all new U joints with no luck

 

i dont know what to tell you, dude. the only other thing i can think of is that the tires or the wheels are out of true...