Vibration when accelerating

I have a 2011 Ford Fiesta I am working on and finally got the clutch replaced and a new 2nd gear synchronizer installed which eliminated the second gear grind.  I did not have much opportunity to drive it before the repairs as the clutch was at the end of its life. Because of this I don't know if the vibration is a new issue or preexisting issue.

It vibrates when accelerating and is relatively smooth at steady state speeds. It seems to be most noticeable in 2nd and 3rd but that is possibly because it passes through the vibration quickly in 1st and by the time I hit 4th I am generally done accelerating. It seems most prevalent in the 2000rpm-4500rpm range. 

It does not seem to be wheel/tire related as I assume it would be present regardless of acceleration versus steady state operation and would get worse at higher speeds.

It does not seem to be any type of engine misfire as I see no codes, check engine light, or other indicators of engine issues. It pulls decent up to 6000 rpm.

At one time I had a 2005 Ford Focus with a bad half shaft and it exhibited very similar behavior but was quite a bit more noticeable then what I have going on in the Fiesta. I could feel slop in the Ford Focus half-shaft so I knew which one was bad and needed replacement. Both of the Fiesta half-shafts feel tight but I have only checked at full droop when supporting the car on jack stands. Maybe I need to check when the suspension is normally loaded? If it is a half-shaft issue, any thoughts on how to diagnose which one is causing the issue? 

Half shafts are the most common answer for FWD and vibration under acceleration. I think you're on the right track. You could also try rotating tires to see if that changes your symptoms.

Inner cv joint is almost always the answer for a vibration on load.  If you can increase and decrease the shake directly in relation to the pressure on the accelerator, it's a real good bet.

Volvo will generally cook the inner joint near the exhaust, and there is often a tell tale strip of old grease directly in line with the large clamp.  

I agree about a worn inner CV joint. I experienced that on an Accord, a CRX or 2, and twice on a MINI Cooper.

Just a quick follow up. I received the axles after much delay due to an error in part marking (I received (2) passenger side axles although one FoMoCo box was marked with the driver side part number). 

The shudder is now gone. Thanks for those that confirmed the likely issue!