Dexron is fine in the old three-speed automatics, but not for four-speed automatics.
Transmissions are designed by the engineers with a specific fluid in mind, and transmission fluids have many different technical characteristics. Using any form of Dexron will cause poor shifting and ultimately transmission damage to any Chrysler automatic with overdrive (i.e., four-speed and higher). Always stick to proper transmission fluids and never rely just on what mechanics tell you, no matter how well-intentioned they are. And never trust a mechanic to put the right fluid in your vehicle -- ask questions and insist on what you know is the proper fluid. You may want to supervise them from outside the service bay!
Of course, there is an exception to every rule. I believe the four-speed automatic used with the 4.0L Jeep engines in the Cherokees and Grand Cherokees used Dexron fluid. While Jeeps are Chrysler products, that particular transmission is an Aisin-Warner model also used in Toyotas and other vehicles. The recommendation above still stands -- find out the proper transmission fluid for your vehicle and stick to it.