94 caravan vibrating

I have a 94 Dodge Caravan with the V6 engine. It has a vibrating problem. Its done this for years but its never caused a problem that we know of. When you accelerate and it hits about 30 mph the car starts to vibrate. There is no power loss, no struggle to accelerate, and it does not affect the car in any other way other than a vibration. It keeps vibrating on up to about 60 or 70 mph. If you just drive at a constant speed this does not happen, so that seems to rule out the tires being unbalanced for me. And if you slow down or let it coast it also doesn't do this, so that in my opinion rules out any warped rotors. It really feels like its coming from the front. Like I said, it doesn't affect the van at all. The vibration can be felt in the steering wheel and you can hear the radio rattling around. It isn't so strong that it jerks the steering wheel around but its enough to shake your hands a little. I'm wanting to guess the transmission.

I'm guessing inboard CV joint. They commonly cause vibrations on acceleration and deceleration.

I thought bad CV joints made that clicking or popping noise when turning.

Inboards clunk and or vibrate on accel or decel, outboards click in turns.

More on CV joints and causes for vibrations: http://www.aa1car.com/library/cvjoint2.htm