Vibration at certain speeds

Jack up the rears on a secure platform and run the truck up to the vibration speed and see if you feel it.

If you do, put a knowledgeable person in the truck running it up while you observe the wheels and tires.

Next remove the rear tires and run the truck up to speed and observe the driveline.

 

You said you had a differential out, what are the chances your read shaft was removed from the slip yoke and put back in out of time? That’s what it really sounds like to me.

Just make sure that cap on the slip yoke and the cap on top of the main shaft line up. If you had it removed and the shaft on the ground, both caps should set level on the ground.

 

Ide check the splines on the steering gear/pitman arm & all U joints on steering column

 

I need help

I have a 2003 international 9400i
480.000 miles had this truck 18.5 years
I have a grinding Is rubbing sound that comes from the transmission motor not sure only dose it at 1300 rpms or if I have a load.
Replaced rear motor mounts clutch and transmission
It's not as bad now but did it today at 1300 rpms
It's got an isx 435

 

Did u joints and yoke
Dose it when going up a hill.
Did yokes all u joints transmission clutch
Rear motor mounts were shot.
Didn't check front