I want to beef up a 2007 Grand Marquis for towing. I’m torn between adding air springs to the rear OR beefing up my standard rear end with heavy duty cargo coils or heavier rear springs. I only want to tow light stuff but want to keep the car for a long time…it’s paid for. Would appreciate any suggestions. Thanks. Gerry, Victoria, B.C., Canada
The springs and shocks from Ford’s P71 Police Package will bolt right in, since the Grand Marquis and the Ford Crown Victoria are mechanically the same. While not designed specifically for towing, these components are beefier and are designed for truly heavy duty use.
The reason the new Crown Vics aren’t rated to tow as much as the older ones is that rear suspension changed in 1998, a Watt’s Linkage was incorporated to the design and the towing rating dropped to around 2500 pounds.
I don’t think simply adding heavy duty springs will safely increase the towing capacity. Also keep in mind the standard rear end ratio for 2007 was a 2.73 which isn’t the best for towing. If you have the handling package (or whatever the Grand Marquis equivalent is) you have 3.27 rear end which is moderately better. If you have dual exhaust then you have the HPP package.
I put in Gabrial Hijacker air shocks in my Ford. I purchased them on ebay for $40 each and installed them both in about one hour. They simply bolt in place of your old rear shocks. They do a great job supporting heavy loads.
You can get some information about Police Springs and stabilizer bars here: http://www.p71interceptor.com/. I do NOT advise that you go that way. Though it will be fine loaded, the car will ride like a lumber wagon unloaded and will not have good traction on rough corners. I would not use air shocks either. The mounts are not robust enough to take a lot of extra stress. Do you have coil springs in the rear or rear air suspension? If the latter, some heavy-duty air springs would help a lot. They are really easy to change out. If you have coils back there, install some in-coil booster air springs. That way you have the best of both worlds. Everyone I have been in contact with likes their air booster springs a lot. They add a very progressive spring rate. I would consider changing the front springs to HPP or Sport coils for balanced handling/steering. Some stiffer shocks would help too.
Note that I have never run across anyone that has gone through with adding true OE rear air suspension to their coil spring car. It would be a lot of work to add the wiring and would be expensive to change the steering/suspension controller and add the ride height sensor.
Note that after 2002 HPP was no longer available on the base model GM. (It left completely in 2008, sadly.) As far as stabilizer bars go, the changes from year to year and the differences between Crown Victorias and Grand Marquis can be very confusing. (Sometimes it seems like they let the assembly line workers decide what to install, but It is not true.) The differences between CV and GM really happened in later models, after 2000 at least. Some info can be had here: http://www.moldyrabbit.com/liquid/index.html as well as at the other link. For specific questions there is a fairly active board with some knowledgeable people here: www.crownvic.net. Be very careful about changing stabilizer bars willy-nilly. You might induce excessive over- or under-steer. If you get matching ones from the front and rear from a different trim line, you should be O.K… Your best bet is to make sure that you have a matched pair from a coil-spring car (police) if you swap them into a coil-spring car and from a air suspension car (Sport or HPP) if you have air suspension. You could also ask advice at
The ?98+ cars have fantastic brakes, but I think that they might have actually been downgraded a bit with the addition of R&P steering in 2003. In any case, trailer brakes would be a good idea.
Be sure to turn off overdrive and follow the severe service recommendations especially for trans and differential service.
I removed the air springs from the rear of a '92 Vic and replaced them with the shocks and springs from a p71 car with no problems at all. There was virtually no difference in the ride. Police car springs and shocks are not truck units. The big rear sway bar on the cop cars is what stabilizes them at high speeds, not the springs…The cop car shocks do indeed firm things up…