Chrysler Technical service Buletin # 21-05-97 applies to your vehicle & symptom. Symptom as described in the TSB: "Transaxle shudder during a 3rd gear to 3rd gear partial EMCC (Electronically Modulated Converter Clutch) engagement, 3rd gear partial EMCC to 4th gear partial EMCC engagement, or 4th gear to 4th gear EMCC engagement. Vehicle speed will be above 40 mph to obtain these shift points. This condition can be the result of worn out automatic transaxle fluid, using additives in the transaxle fluid, or from using the wrong type fluid (Dexron II, III, or Mercon) in the transaxle."
A lot of technical language, but if you experience the vibration as trans shifts from 3rd to 4th, esp going uphill, I bet this TSB is the answer.
I have driven many Chrysler vehicles that had this symptom. It often happens over 40 MPH & often while going uphill. The whole car shudders.
The procedure for this TSB is to merely do a "normal" transmission service (dropping the transmission pan, changing the filter, sealing pan & refilling transmission)--w/Chrysler ATF+2 7176 transmission fluid (No other brand should be used) & a genuine Chrysler transmission filter.
This will probably solve your problem & if no, then at least it's not an arm & a leg & maybe you're due for a trans service.
Please post back!!!