Let's Play 'Swap a Front Suspension' - Plymford Edition

High up on the list of issues on Plymford is the increasingly decrepit state of the front suspension & steering system.  For those who haven't followed the whole build, the chassis is basically a 1975 Ford LTD.  It's a big, heavy, fully boxed frame with an integrated front crossmember, rear steer with a pitman arm and steering box.  Basically, its a truck.  And the steering has been de-powered, poorly, which means it has about 1/4 turn of play on center and takes two hands and a leg to turn at parking lot speeds.  

My first thought was to swap in a whole front suspension crossmember from a 2003-11 Grand Marquis.  This would solve a whole bunch of problems:

A) it moves the steering to the front, which means I can replace the stupid, leaking, weird, home-fabbed oil pan with a stock ford truck rear sump pan.

B) it gives rack and pinion steering which I can power with a hydraulic pump

C) More standard ford front suspension bits and brakes

it would change the bolt pattern to 5x4.5, which would mean swapping the wheels and running adapters in the back (which would still be 5 x 5) or redrilling the axles for the smaller bolt pattern.  Minor issues.

Unfortunately, I had a buddy measure the frame rails on said Grand Marquis and the outside-outside dimension was about 36".  The LTD's frame rails are wider- almost 40" - so a significant amount of fab would be needed to modify.  Plus, the way the engine mounts would have to be changed.  There's a 460 big block & C6 there now, and the plan is to keep that drivetrain, for now anyway.  Despite having a narrower frame, the Grand Marquis has a wider distance between the steering arms and ball joints.  So it seems the upper and lower control arms are longer.

I could swap the whole front part of the GM frame, but that would require even more work, remounting the body and radiator, etc.  The roll cage on Plymford is welded to the frame, so swapping the whole frame is a no go.  

Another option could be to keep the LTD's suspension (overhauled, with new bushings) and swap in everything between the ball joints.  This would require some fab work, and suspension geometry figurin', none of which I'm opposed to.  I'd have to figure out how to mount the rack, again, not a huge deal, and the anti-roll bar mounts.  The engine mounts could probably stay the same.

Apart from these ideas, anyone got any other ideas for a front suspension swap/ reconfiguration, that gives a) rack and pinion front steering, and b) uses mostly off-the shelf OEM stuff?  

volvoclearinghouse said:

Apart from these ideas, anyone got any other ideas for a front suspension swap/ reconfiguration, that gives a) rack and pinion front steering, and b) uses mostly off-the shelf OEM stuff?  

C4 corvette.  front steer, quick-ratio rack, 13" rotors, twin-piston 40mm bore calipers, aluminum UCA LCA and Knuckle.  crossmember is a bolt-in to the C4 chassis, only the upper shock mounts will require fab.

biggest negatives:

1. you'll probably want to ditch the transverse leaf for a more conventional coil-over setup.
2. wheel bolt pattern is 5 x 120 (approx 4.75")

In reply to AngryCorvair (Forum Supporter) :

C4 front subframe is nearly 10" narrower than his current frame though. The UCA mounts are about 29" apart, the subframe mounting flanges are a couple inches wider on each side but not much.

But, that's something I never would have thought of.  Appreciate the ideas, keep 'em coming!  Once my Jaaaag is off the lift, and I get the trailer hitch installed on Mrs VCH's new ride, this will probably be the next project.

In reply to RacetruckRon :

Well, that certainly puts a damper on things. I was gonna measure when I got home.

RacetruckRon said:

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In reply to AngryCorvair (Forum Supporter) :

C4 front subframe is nearly 10" narrower than his current frame though. The UCA mounts are about 29" apart, the subframe mounting flanges are a couple inches wider on each side but not much.

Can the C4 subframe be 1: sliced and widened or 2: discarded of in favor of a welded steel replacement?

Hmm.  Sounds like the 460 fits particularly well in the 03+ crown vics/ GMs due to the crossmember arrangement.  Perhaps that would be the way forward after all.  The main issue would be notching/ reinforcing the existing LTD frame to fit, but I've got a 240VAC welder now, I can do anything.  

tuna55 said:

RacetruckRon said:

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In reply to AngryCorvair (Forum Supporter) :

C4 front subframe is nearly 10" narrower than his current frame though. The UCA mounts are about 29" apart, the subframe mounting flanges are a couple inches wider on each side but not much.

Can the C4 subframe be 1: sliced and widened or 2: discarded of in favor of a welded steel replacement?

One issue with widening it is then the steering rack would be wrong for width, and things like bump steer and maybe Ackerman.  All fixable, in theory, though.

volvoclearinghouse said:

Hmm.  Sounds like the 460 fits particularly well in the 03+ crown vics/ GMs due to the crossmember arrangement.  Perhaps that would be the way forward after all.  The main issue would be notching/ reinforcing the existing LTD frame to fit, but I've got a 240VAC welder now, I can do anything.  

I would think that this would be your easiest bet. Especially if you'll end up with closer track width/simplicity on other things. Reinforce the frame somewhere above it, bring frame "in" to meet the CV Subframe, and then notch out frame to clear new suspension as last step. 

I have been doing a fair bit of IFS research lately, but all of them are too wide for my application, so i've been thinking through the exact opposite of what you are.

I love the C4 suspension I grafted onto my minitruck but hate the limited wheel options.  I would be looking hard at how to make newer Crown Vic stuff work with your frame.  It's a lot newer and designed for a heavier vehicle than the C4 bits were.

Solid axle, cut and welded for static camber. Gasser that baby!

Are there any other FoMoCos from that erea with similar front end parts and compatibility? Or I guess, being a 75 full size, there's no crossover with a performancy car?

If you feel inclined to move forward with the CV front setup I have the crossmember, steering rack, upper control arms, sway bar and struts sitting here (basically everything but LCAs and spindles)  All from an 03 Marauder.   If you find yourself coming to NC anytime soon they are cheap for the taking.