Crankcase (pcv) problems of the 2008 Jeep Grand Cherokee

Wife traveling with son on fwy at legal speed of 70 mph w/cruise control on, car suddenly decelerated causing a violent maneuver forcing car into neighboring lane and almost crashing. She stated it was as if it suddenly downshifted into lowest gear and brakes applied forcefully. Regaining control she deactivated the cruise control and proceeded to destination at 50 mph. Took to dealership in davis where it was diagnosed as catastrophic failure of the transfer case which was then replaced at the cost of $2842. 75. She retrieved car two days later and proceeded to drive back home (distance is @ 178 mi one way). Car repeated sudden deceleration upon entering the fwy and getting up to speed. Continued home due to medical appointments to keep. Kept cruise control off but called dealership to report that replacing the transfer case did not solve the problem. I pulled codes upon her arriving home and found only code 0430 (catalyst system efficiency below threshold [bank 2] indicating the converter not working to specs. Today she was returning to davis to visit with grandchildren and experienced the same situation. At 70 mph car suddenly decelerated rapidly (as if brakes were applied forcefully) and caused her to abruptly move into the lane to her left. She regained control and continued on at 50 mph. The dealership informed her no mechanics would be available until Monday but as she has a flight out of lax to catch early Monday a. M. She decided to continue on to l. A. Without using the cruise control and proceeding at slower speed. The power steering pump was replaced on 4/15/2013 at dealerships recommendation due to a leak and the transmission was serviced in addition to having new valve cover and gasket put on. Spark plugs replaced, throttle body and combustion chambers cleaned and pcv valve replaced. Internet research indicates this is a repeated problem with the Jeep Grand Cherokee.