Piston Slap: to Mark VIII the Mark VII Air Suspension

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TTAC Commentator furiouschads writes:

A Mark VII is in my sights.  I like the Mark VIII air suspension control that lowers the car when it hits 60 mph.  Will a Mark VIII suspension control box work in a Mark VII?

Sajeev answers:

WOW: you mean someone actually can afford to spend the $300-2000 in new/used/aftermarket/OEM replacement parts to make a functional Lincoln air suspension system on a fully depreciated hooptie? You mean someone else out there doesn't pigeonhole these systems with the nightmares made by manufacturers in a more European locale?

So sure, why not lower a Mark VII air suspension at speed?  I poked around the wiring diagrams for a 1988 Mark VII and 1993 Mark VIII and wasn't totally horrified at what I saw.  Matter of fact, I'd be tempted to integrate the 1982-83 Fox Continental variable ratio steering system into it, as the Mark VIII's air suspension "control box" also controls its speed sensitive power steering.

But being a complete Fox Body geek isn't a great idea –welcome to my hell!– and adding the Mark VIII's lowering capabilities is already challenging.

1988-1989 Mark VII LSC

It isn't easy because the Mark VII air suspension is a different beast: boasting the same number of ride height sensors (two front, one back) but each sensor has an extra (4th) wire. The reason escapes me, as someone ran off with my Mark VII service manual. While it might be possible to convert to Mark VIII sensors, hopefully that isn't necessary.

The "hard" part is actually the easiest: the lowering feature comes via communication to the VSS (vehicle speed sensor), readily available at the engine computer (in the kick panel, tough) or speedometer (easy).

If you get a Mark VII that isn't hopelessly in need of attention, get a Mark VIII suspension computer and mock it up. After you get the shop manuals for both and do a good job with RTFM…son!

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you're in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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