Regular cab begins to vibrate while driving

It just started today when I went to pick up my wife. I noticed my truck was vibrating mildly but didn't think of it since I live in an unpaved neighborhood and the roads are covered in ice. When I got to the highway that was clear the truck had started to vibrate pretty bad. It was short quick and repetitive vibrations that only stopped when I took my foot off the throttle while going 35 mph. I thought it was my diff so I drained and refilled it then performed a much needed tune up. It lessened but the truck still vibrates. Is it possible I have a bad motor or transmission mount?

 

I would start with getting the tires rebalanced. Bad mounts shouldn't make the truck vibrate. More of a clunk when first accelerating or decelerating.

 

If it was my tires then it would be a constant vibrating. My truck only stops vibrating when I let off the throttle completely