Dear Tom and Ray,
You are slowing down!! Her tire pressure may be a problem, but when you suggested she buy a tire pressure gauge, you neglected to point her toward you shameless commerce section. I have bought your beautiful, pleasure to use, analog pressure gauges for my adult children and myself. Great gauge, feels good in the hands, nice valve for adjusting pressure! Your boats must be paid for! jkd
Dear Tom and Ray,
As a long time Crown Vic/Town Car air ride user, the most common solution to hard ride after shock replacement is (drumroll) new shocks. It is true that high tire air pressure will also effect ride and should be at the car pillar psi for best ride. However, the factory shocks are softer than almost all aftermarket shocks, so going factory again will return the ride. Many, many people have experienced this when going aftermarket on these cars.
Tires ARE an integral parts of your suspension. The size, the type, and the air pressure,they matter. Many customers with these big 20" rims have a low profile ( 40 series or so ) on a vehicle that had 16" rims and 70 series. They very quickly find a major difference in ride quality. On my own truck I had BFG all-terrain T/A and what rocks they were to drive on. I experimented with pressures down to 30psi then changed tire type to a light capacity firestone wildeness and immediately felt a ride difference.
They may have installed heavy duty police car suspension parts which could make the car ride rougher, since most of these cars say Police on the side.
That is exactly what I was thinking when the question was first posed to Tom and Ray. I also believe that police-grade shocks may have been installed in her car.
I had three thoughts after hearing this exchange. First was that, as other mentioned, they might have installed police/taxi shocks (they are the same thing). Second, the tire pressure before the shock change might have been chronically low and they were used to it. Maybe the shop just brought the tire pressure up to spec. Third, I would be surprised if a 2004 needed shock replacement unless it had an extraordinary number of miles on very bad roads.
Extra notes: Relatively few Crown Vics or Grand Marquis have rear air suspension. Some with RAS are HPP models with relatively stiff springs, shocks and anti-sway bars all the way around. The HPPs have a very nice suspension for spirited driving with a passenger sedan.