Required fix was the replacement of the number 4 cylinder head, gaskets, rocker arms, exhaust and intake cam phaser, and engine cylinder head bolt.

The vehicle was taken to my usual mechanic, who runs a relatively small shop. They stated that they have dealt with this exact same issue no less than 6 times in the past year on the pentastar motor. They also stated that when ordering the parts from the dealership that this single cylinder head is in stock. However the other cylinder heads are not in stock, which would appear to represent that this is a common problem specific to the number 4 cylinder in the 3.6L V6 pentastar motor.

Purchased 2014 diesel Grand Cherokee in Sept 2014. In June set out on 400 mi vacation drive and experienced shudder at about 45 mph on interstate for a couple of 3 or 4 second bursts. Coasting or speeding up appeared to make it go away. Turned around and had dealer check and said needed new cat converter. Ordered part and said go on vacation that it would be okay to drive. 2 weeks later returned and new cat installed. This solved the mil light(check engine) issue and has not come back on at 14k mi now.

Shudder problem continues intermittently. Found service bulletin that says fix is replacing cylinder heads with redesigned ones. The parts are apparently on order but 3 weeks and counting. This is major engine work and hope if and when it gets done the problem is solved. Of course that could be months before can be confirmed.

Update from Mar 12, 2020: It is now about 5 years later and the redesigned head actually solved the problem. Only issue since then was a thermostat failure in 2018 that cost almost $600 with labor. Remember the days when a coolant thermostat was a minor fix that anyone with minimal skills could replace? Even though have extended diesel warranty they find reasons stuff is not covered. Check engine light came on recently and dealer said required injector cleaning. That cost about $771? Since they reflashed the engine to comply with diesel settlement the mpg has dropped by 3 mpg and power is decreased and more turbo lag. Don't want another car payment so will hold onto but when time comes I will be buying another brand. I have owned a Chrysler, Eagle, Dodge and 2 Jeeps. The 67 Dodge Dart was pretty reliable but the rest not at all.