center shaft bearing question....

how do I know it's going out?should I be able to grab dish after moving around in the support rubber boot?

I have a very strong vibration between 1000 and 1500 rpm that shakes the truck

2009 4.0 liter 4 by 4 with a hundred twelve thousand miles, no shake or vibration anywhere else just at that rpm range

 

Would not be rpm related but speed related. Are you lifted?

 

No actually it does seem to be at that rpm, speed fluctuates depending on uphill or downhill. Truck has a 3inch lift which was installed at five thousand miles never has had this vibration before until the last 10 days my list is a toyotec

if I just give it gas and go right through the RPM faster there is no vibration but if I barely give it gas and get it to that rpm the vibrations starts
and it's extremely obvious