I own a 1999 Dodge Durango 5.2 V-8. In the summer time when the AC is needed, the car shifts violently. This happens only when the AC is on. It will get up into the 4 and 5 thousand RPM range before shifting. After a while of doing this, the check engine light comes on but goes off quickly. No one in my area can seem to find the cause. PLEASE HELP if you can. Thanx!