It's not the drive shaft. It feels like something might be lose between the engine and the pedals. I'm gonna get under the car soon and have a good look around. Possibly the heat shield or something around there. Il keep you updated if I find anything.

 

I feel it while slowly going past 30mph and feel it at 40 mph. Once I go past 40 the vibration stops.

 

Exhaust vibration heat shield plates can carry through the frame and resonate in places. Check if any exhaust pipe or muffler from engine to the back is lose. I have an audible vibration from my H2 exhaust I can hear on acceleration. It's the exhaust cause I had the exhaust on my excursion switched over to dual and that was when I heard the same noise. So in my case it's from either the muffler or pipes.

 

Finally I found the problem. While driving the other day I broke a cv joint (car only has 21000 miles). I managed to get the it on a ramp and realized the bolt holding the top of the diff in place was missing. The vibration I'm guessing was just the lose bolt and it finally losened all the way or snapped off taking my cv joint with it. I was only traveling at a low speed so I was lucky nothing else happened. I've put a new bolt in and tightened everything up and now no more vibration. I'm getting a small cracking noise when hard breaking or turning at low speeds. The bottom diff mount doesn't look so good so that's my next job but I'm nearly positive it will solve my problems.

Will update you all once I've changed the diff mount.