a misfiring engine will make the entire rig shake like crazy...it's happened to me...
just pull the plug wires, one at a time and check for water intrusion...
if it all looks nice and dry, move on to the next theory...
:confused:
I don't recall seeing if you stated that your MIL is lit...
I had something similar happen when I had my 94. I had water on the plugs...which cause the engine to fire on 4 of 6 cylinders.
check your plugs/wires.