Vibration Problem. Please help

[e.starkey65]

I have a 2004 Ram 1500 4x4 with a 4.7. At first my check engine light came on and I had a cylinder 3 misfire, which was causing my truck to jerk while I was driving it. Now my check engine light is no longer on, though I did not repair the issue. Now it seems that I have a separate, or potentially related problem. My truck is now vibrating. Sometimes it starts around 20 mph but most of the time it does not start to vibrate until about 40 mph. This issue also continues to happen while I'm driving if i put my car into neutral and coast. I did take my truck of road the day that it happened. But I didnt do anything extreme, although there was a good jolt from a pothole but i was moving very slowly, maybe 5mph tops. So I didnt think that would be enough to damage the axle or such? I'm wondering if maybe it could still be my spark plugs misfiring, but in a way thats now causing a vibration instead of jolts? I took it in and had the tires balanced and rotated hoping that would be the problem but it didnt help. I've also read it could be the u joints or another problem with my drive line. However I'm not mechanically savvy enough to hunt out the problem on my own. If i knew the problem I could fix it myself, but I dont know enough to find the problem. Any ideas on what the issue could be, or help on how to go about finding the issue? All help is greatly appreciated!! thank you