I have a 1999 durango slt 5.2L 4wd. I will be driving at 50 - 55 mph and the truck Will randomly jerk like a quick single misfire. No engine lights come on but i don't think it's the tranny beacause the rpm doesn't change. Its a random single heavy jerk at about 50 - 55. It Does it with od on and off as well. Yesterday I had misfire code on cyl 2 and 7 but now no codes or lights come on and is still jerking at 50-55.

 

Check the miss fire count? See if it is miss firing at idle or only when it under load. But if it is that intermittent i might look at the injector pulse with also.

 

Could be as simple as a bad load of fuel or time for a set of plugs.