up hill vibration

What is your question?

My 1997 Dodge Caravan 3.0 started vibrating when going uphill. This did not happen for the entire hill climbing. I had someone rev the engine while in drive and the engine would rise up a bit more than usual. I carried it to a mechanic and it turned out to be the engine mounts. After the new mounts were installed it was OK for about nine months. Now it has started doing the exact same thing except this time the engine doesn't rise as much. I have had two mechanics check it and both say it is not the mounts. One said he did not know what was causing it. The other (Who happens to be the one that did the original work) could not spend time checking at that time and told me to make an appointment and bring it in later. Can anyone give me an idea as to what the problem is so I will have some idea if what I am told really could be the problem. I beleive in "Trust but Verify". Sorry about the long story but didn't know any other way to explain my problem. Thanks