Truck Driving Rough After Changing Rear End

Sounds like something may have come loose. Check to make sure that the nuts on the yokes are tight. Also check the nuts/bolts on the u-joints. And check the fluid level.

 

Why change the rear end?

 

Did you replace with new, rebuilt or used?
Automatic or Manual transmission?
Does the system have proper air pressure?
Did you inspect old rearend and determine what broke?

 

Planetary? Real heavy spec then?

My thought would be wondering how clean the housing was, and if some metal made it out to the planetary.

 

Like a previous poster suggested make nothing is coming apart. Check the thru-shaft output bearing as well.
Buy a new magnetic drain plug, get a drain pan and swap out the new drain plug with the old one. See if there is any debris on it or in the oil that came out. There will be a small amount of fine metal no mater how good a job the person who replaced the diff of cleaning the housing.