My 1984 Mercury Grand Marquis rides on an uneven keel
The rear of my Grand Marquis has been leaning downward to the left (approx 1.5 inches) since I bought it. At first, I attributed the list to the usual slant roads have to have so rainwater can flow off. That wasn't the case, however.
My next guess was that the 30 year old springs may simply have become soft with age, so I had all of them replaced (front and rear) with OEM specification Moog coils and installed new shock absorbers, too, (and what a good idea that was since the old ones were suffering a bad case of rustout).
The new springs and shocks have made the Merc ride and handle wonderfully comfortable again, but the list is still there. I had the frame checked, too, but it's not bent or otherwise deformed.
A member of the community has kindly suggested that the lean may simply be an optical illusion, but my tape measure check doesn't bear it out, unfortunately. The Merc's left rear side sits almost exactly 3 centimeters lower than the right - or the right side is 3 centimeters too high above the ground, which seems likelier the more I look at the car.
So, I'm still puzzled and in search of ideas. Thanks a million.
3 cm - your not from the states -eh! You've checked everything that is suspension related so it can't be anything to worry about. Move that 50 kilo tool box that you are toting around back there from the left to the centre and see what happens.
I had a similar problem with my '90 LTD Crown Victoria - just the other way around (list towards passenger side). Since I couldn' t figure out the cause either, I installed a set of new Monroe load adjusting shock absorbers type SensaTrac at front + rear and fit in 2 coil spring adjusters into the rear RH coil spring (avalable for front & rear springs - see ACDELCO Part # 45K12002 / 45K12008 / 45K12013). This workaround actually solved my issue; ride comfort is as good as it was before.
One question: where exactly did you measure ? I measured the clearance on top of the wheel arches. Do not measure e.g. at the bumpers. These are just bolted to the frame and you never know if they are leveled well. Another tip: make sure the ground you have parked the car on is level and even during measurement. Also remove heavy objects located on the affected side of your car / trunk. These things may have a significant impact on your measurement !
At least I'm not alone in thinking about that 50kg toolbox back there, and point about the tolerance of bolted on parts is a good one.