I agree with the others. I have seen this on a 1990 Grand Caravan with 3.3L engine. I got severe shaking when accelerating (gravity was a factor only in the sense that I had to add power to maintain speed). It felt like the steering wheel was shaking, as you describe...as if the wheels were pulling alternately instead of together. I had a hunch it was drivetrain rather than steering because of the only symptom - the problem vanished as soon as I let off the gas. I feared transmission, maybe steering rack, but hoped for cv joints. A few mechanics were stumped, which was a problem since I was 1000 miles from home with plenty of hill climbing ahead of me (in Montana, headed for California). One shop told me flat out it was not axles and admitted to no other ideas. Another assured me it WAS an axle, so I gave them a shot. 3 hours later I was happily (and smoothly) back on the road with a new axle (cv joint). I'm again noticing the beginning of the same symptom. It's been about 6 years for that axle, a little premature but oh well. This car doesn't leave town any longer, its last trip was a year ago, so when it gets bad, I'll spend a couple hours changing it. BTW, a Napa store employee mentioned something about premature cv joint failure resulting from some kind of poor alignment of the engine related to misaligned motor mounts, and indeed, at the beginning of my trip I had a new front motor mount installed (thinking that was the source of the problem which turned out to be the cv joint). Perhaps the mechanic did not get the engine precisely positioned. I have no other confirmation of that point, but there may be some information in the factory manual on this. You might want to see what you can find out about this for your 1996.