rack n pinon swap

[gaddy 1]

hi i'm  wanting to put rack n pinon on my 70 challenger i'm a machinist by trade and fabicator ,my question is what rack n pinon from another car will work

[Brads70]

I've done some investigating on this. You would need a rack with a 26.420" pivots , custom racks are available. Common, Mustang based racks use 24.250"  There are parts available to lengthen the pivot points . https://www.summitracing.com/parts/hdt-mp-039-4. I was considering this and shortening it?
Bigger issue is the stock steering arms won't work. What's needed is a custom steering arm that uses a screw in ball joint with the steering arms corrected for use with a rack. Or a different spindle set up altogether. Or make a custom k-frame with the corrected geometry. Not impossible to do but a ton of work to make right as it needs to work with the fixed upper control arm mounts.
Mopars can be made to handle quite well using the stock design. 
I was gathering parts to build my own k-frame  but gave up on it when after using aftermarket parts based on the stock design I was able to get my car handling much better than stock.
I'm now using the flaming river rack I bought in my Javelin project.
Bumpsteer and the rear track width bigger than the front are E-Bodies biggest issues IMO. too soft spring rates and sway bars are easily addressed with aftermarket suppliers.   

[Chryco Psycho]

Welcome to the site BTW
I agree you can go a long way with the stock design & upgraded parts , R&P are not easy to set up correctly in an E body .

[1 Wild R/T]

And don't get sucked in to buying the poorly engineered bolt in rack kit from Unisteer...

[MoparLeo]

Remember that a R & P is just part of the front steering/suspension system. Change one thing, 2 more problems crop up.
Millions have been spent in R & D on these steering set ups. Unless you just like to fiddle with things, there are complete front bolt in suspensions that have had all that time and money spent by someone else to come up with a "system" that works. These eliminate the torsion bars as well. Not everything is based on a Mustang II. AlterKtion, Gerst etc... How many current cars of ANY brand use a coil spring suspension ?

[1 Wild R/T]

Remember that a R & P is just part of the front steering/suspension system. Change one thing, 2 more problems crop up.
Millions have been spent in R & D on these steering set ups. Unless you just like to fiddle with things, there are complete front bolt in suspensions that have had all that time and money spent by someone else to come up with a "system" that works. These eliminate the torsion bars as well.[/font]

  Yeah, Ford.... When they were designing the Pinto.... Since thats the predecessor of the Mustang II & where the Mustang II suspension came from....  Which is what most of the replacement coil over front suspensions for Mopars are based off of....

[anlauto]

I would just buy a complete aftermarket kit if it's truly what you want

[HP2]

As Brad pointed out, the biggest issue fitting a rack that will work properly is getting the correct length and then fitting it in the same space the oil pan wants to occupy to mate with the stock steering arms. To avoid this issue you need to front mount the rack, which can't be done with the stock lower steering arms.

If you want improvement without all the fabrication work, the Borgeson steering boxes provide improved on center feel, better overall feel, and lighter weight.

[anlauto]

Not to mention the simple fact that most racks are designed for front steer applications and E-Bodies are rear steer cars.

[gaddy 1]

I see no one has attempted this but from doing my own research I'm reel sure i have well i know i have the mount fab'ed up and found a very close rack length.. i do appreciate all the comments were to purchase or to buy, but I'm not that kinda guy any thing is posable ... i'll post my pics... thank ya.

[rftroy]

No...it's not that no one has attempted this.  The principles of suspension geometry, and an analysis of the E-Body factory suspension shows that you can't just mount a rack wherever it will fit and get it to work.

A steering rack system typically has a rack with pinion gear inside a housing, and two tie rods that pivot on the ends of the rack.  The outer ends of these tie rods have ball joint ends that attach to the steering arms on the spindle.

If you leave every part of the factory suspension in place, and remove the stock steering box, pitman and idler arms, center link and tie rods to install a steering rack, the inner tie rod pivots on the rack must be placed in the same location as the original location of the factory inner tie rod ends. 
If you take a look at the stock suspension, and try to look along a line between the left side and right side inner tie rod ends, you will see that, as stated by HP2, the rack will need to pass through the oil pan to be properly located.  Actually, it would probably need to pass through the crankshaft.  This is why the E-body center link has the dip in it to clear the oil pan.  But a steering rack is straight.

Moving the rack lower to get it to fit, you would lower the location where the rack arm pivots should be.  The geometry will be off and you will get bad effects, primarily in the form of bump steer.  The amount that the tie rod inner pivot would be displaced would be substantial, and would cause extreme and dangerously unstable wheel motion in operation.  This is what Brad70 was alluding to when he said you would need custom steering arms.

This has been looked at by a lot of people over the years, and the only way to go to rack and pinion involves complete redesign of the entire front suspension by a qualified engineer and lots of money.  And that, as has also been stated, has already been done and exists in aftermarket form.
I will also throw my vote to keeping the original gear.  The Chrysler factory system was actually quite good and can be stiffened up a bit in a few spots.  You can get help on that from people on this site.

Good luck,
Robert

[RUNCHARGER]

How will you check the Ackerman?

[HP2]

The problem with "very close" when it comes to suspension geometry is that a slight variation in the location of one part can be multiplied by the time it hits the pavement contact point. When it comes to angles, you can miss by an inch and it might as well be a mile.

However, numerous cars out there have bump steer problems. If your car gets worse bump problems after conversion, you likely can still learn how to drive it to compensate for the issues it introduces. It may not be ideal, but it certainly can be livable.