2008 RAM 1500 4.7L. When cruise is set at speed (ex 70mph) speed is maintained on level ground at approx 2100 rpm. When a hill is encountered the speed will fall off to approx 65 mph and the engine then speeds up to 3500rpm and accelerates back to 70mph. If I step on the accelerator when approaching the hill to maintain 70 mph, then rpms increase to approx 2600rpm and speed is maintained even when I take my foot off the accelerator, unless the hill is very steep, in which case is make increase engine speed to 4700rpm or higher trying to increase speed back to the set speed. When recently driving in very windy conditions, the cruise was unable to maintain speed and constantly decelerated 5mph, jumped to 3500 rpm from 2100 rpm, accelerating back up to the set speed, dropping back to 2100rpm and repeated the process again and again making for a very stressful driving condition. Question is if this is normal operation or a possible problem?

 

It's gear hunting. Check the source vacuum for the cruise servo, make sure the line is intact, no cracks, leaks, etc. anywhere.