rumble-strip-like vibration on 1995 Ford Crown Victoria

When going about 30-40 MPH uphill, it feels like I am going over a rumble strip. Told it was misfiring, I had new plugs and wires tuneup. Still did it. Had tires rotated, This helped 80%, but still it's there. What else could it be?

2 answers
Have the tires checked as it could have a bubble or the tread could be separating
I had the same problem last year. Take it to a transmission shop and get the fluid changed. I think this will take care of your problem.