I have little clunk once in a while when backing out of the driveway but last night the disco start shaking on acceleration and now it seem a bit more intense. it is not related to engine bec. the disco idle normal and doesn't appear to be related to ignition. 127K miles.

 

Sounds like a drive issue. Check all your ujoints and check the rotoflex coupler on the rear drive shaft. Have you had your front driveshaft rebuilt?

 

havent change it yet but I got the fron drive shaft off, so I need to replace the rear u joints also? Thanks.

 

Yeah ujoints and the rotoflex coupler need to be checked. The rotoflex can look ok but not be so pay close attention to it

 

So, have you rebuild your front shaft, how often do you grease your u-joints and are you stilling running the original roto-flex?
When was the last time you drained and refilled the diff's and t/case while looking for metal?
Since you have a CDL, you might want to run 1 shaft at a time to see which one is causing the problem, and what ever you do, do not go far from home or get above 40MPH or you will probably have an expensive failure to deal with.