Technical Cross Steering Where to mount box?

61 Falcon G***er, 65 Chevy G10 Van axle.
To move the drag link in front of the oil pan, I’m moving the stock falcon box to the front of the frame and flip the pitman 180 degrees pointing backwards. Since the stock falcon steering was rear steer, forward facing pitman, it will steer the right way with front facing steering arms with a rear facing pitman. The front steering arm on the p***enger side will turn the right tire, the original van axle rear steer arms are connected with the factory tierod.

My question: how far forward to mount the box?
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Do I mount it where the pitman pointing straight back is even with the steering arm on the wheel that&#8217;s pointed forward? This would have the pitman-to right wheel drag link perpendicular when the car goes straight, but angles front/back during turns. By "perpendicular", I mean across the front rear axis of the car (or parallel to the axle if you'd rather think of it that way).
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Or do I move the box back a bit so that the drag link is not at perpendicular during straight driving and p***es through the perpendicular when turning? If so, is there a rule of thumb, formula, or steering angle to shoot for?

 

Maybe an engineer/physicist will chime in to the contrary, but I don't think it will matter a great deal either way. Because, it will always be "off" at some point.

That said, were I doing this, I would keep it parallel (figure 1) in the straight ahead position.

 

I'm just afraid there's some issue with the steering rate or other issue that might creep up when the steering is at full lock.

 

I'd go with #1 too.

 

It seems to me the steering rate would be affected most if the pitman arm were not parallel with the centerline of the ch***is. That would change the effective length of the pitman unequally left to right. But that is a separate issue not raised here. In this case, there may be some geometric effect if the drag link is not perpendicular to the centerline, but I just can't visualize that.

Ask your self this.....on stock suspension/steering geometry for vehicles with cross steer, how do the OEM boys do it? I know I have seen rear steer with the pitman arm forward of the steering arm tie rod hole, BUT that has been because they used a intermediate tie rod and idler...and, as I recall, maybe incorrectly, the outer tie rods were behind the intermediate rod, putting them pretty much in line with the steering arm hole.

The same thing occurs with front steer systems is most cases, only mirror image. Come to think of it, the one cross steer system with a drag link I have had some experience with is Jeep Wrangler, Cherokee and Grand Cherokee. They are front steer boxes, the drag link is ahead of the tie rod and at a slight angle from perpendicular, the pitman arm end slightly ahead of the other end, but not by much. I believe that is to avoid any possibility of interference with the drag link & tie rod during full lock turns.

Since you are using a front mounted drag link and rear mounted tie rod, you will have absolutely no interference with the tie rod position changing because of Ackermann in the steering arms.

Again, I cannot think of any reason why perpendicular would not be just fine.

 

...did mine like your #1 idea, works great.

 

I agree with everything you've said here. I have looked under my own Cherokee and have thought about copying it but that stupid jeep y type steering made me wonder how many comprises are in that design. Since I don't havt to worry about tie rod interference I wondered if I should strive for a drag link that doesn't stray far from perpendicular.

I know that figure one's drag link will move further from perpendicular than the one in figure two. Especially if figure two p***es perpendicular exactly halfway between straight ahead and full lock. Or am I over thinking this.

 

Thanks to all three of you guys. Good to get some advice this quick.

 

Everything works when parallel and at ride height, ground and draglink.

 

I woke up thinking about this. I agree the arrangement shown in figure 2 will result in the drag link diverging TOWARD parallel when traveling from lock to lock.

Whereas, the geometry of figure 1 diverges AWAY from parallel when traveling from lock to lock. And, with the length of the drag link being what it is, the actual angularity in figure 2 may not be as much as the illustration suggests.

I still think it would not make a lot of difference either way.

By the way, the second generation Grand Cherokee used a separate drag link, not the "Y" style used on regular Cherokees. I was thinking of the Grand version when I commented on Jeep's configuration and forgot that Wrangler/Cherokee was not the same. I think the "Y" version may create some toe variation with suspension travel whereas the totally separate GC style drag link/tie rod maintains consistent toe throughout suspension travel. I think in normal street use the "Y" style toe variation is minimal and when off road and utilizing greater suspension travel, the surfaces are usually poorer traction and speeds low.

One other characteristic of the Jeep front ends is little or no Ackermann. Those puppies scrub a lot in turns and tire squeal in tighter turns is common. Neither of your configurations suffer that problem.

 

ok,...most of the time you are driving, are you going strate or are you turning?

 

That’s what I was thinking as well. Figure two, if set up parallel to the axle when at the mid-point between straight ahead and full lock would tend to limit how far away from parallel the tierod strays to the minimum; whereas figure one starts out perfect and only gets worse from there.

But, as Rusty1 pointed out, he set up using figure one and had no problems, so maybe it’s a moot point at the angles experience during normal steering situations.
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The van axle was originally side steer and the wheels can turn a ridiculous amount before hitting the steering stops, so my concern was that there could be issues at full lock if I used the setup in figure one.
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Thanks everyone for your input!<O</O

 

good point- i think i'll probably end up with a mock up like Figure 1 and only stray from it if i notice an issue at full lock. I'm probably overthinking it, but it's my first build where i get to set up the geometry myself and didn't want to make a stupid error.

 

I'd toss the stock Falcon box. Not a good choice for the project, and many other boxes that work better. Location up front depends on where the end of the pitman arm sits, and I try to make a straight line that's parallel to the axle with the drag link. So situate the box where the end of the pitman arm point level and parallel to the axle when attached to your steering bracket on the backing plate.
I used a late 70's Courier PU steering box, as I had it leftover, and it sits outside the frame rail. If room isn't an issue, then newer Ranger boxes are the same, but sit inside the frame rails. Either are cheap at the junkyard, and I gave $30 for mine.
I went with a '95 Camaro column in mine, as I didn't like the Falcon column, nor the Ford fuse box on the headlight switch. Going with the GM column allowed me to get a wiring harness for GM, and use a GM headlight switch, so column and headlights were plug in connectors, and have a modern fuse block that's easily accessible.

 

I've removed the column, and will run the shaft with a ujoint and heim supports.

It's a nice compact box and my Small Block Mopar with alloy heads and intake should weigh much less than a SBC. The engine setback helps to.

Wiring's not an issue, as it's going to be wired as a racecar.

Why do you not like the Stock Falcon box?

I like your Falcon!

 

I didnt even read answers but have always been told on "STREET DRIVEN" cars the "IDEAL way is at wheels pointing straight forward tie rod & drag link parallel & the same height with motor installed now as we all know there are thousands of cars that arent even close to that configuration that have logged many miles so not out to argue this point

 

If the pitman arm goes past 90* ( or over centers ) you'll have trouble either way- anyway- always

 

Very true-but i'm hoping there's not much chance of that.

I guess there is "possibly" a chance that if i set up Figure one, during a hard left turn, the pitman could potentially pull the drag link and the steering arm inline with each other and not want to return to center.

Again, i'm probably being overly dramatic about it.

 

You'll need to be on the steering stops before the pitman over centers.
That's all in the length of the arms- steering arms and pitman arm.
You mentioned the extreme turning of your axle. It will need stops that prevent the geometry from over center condition.

 

Just mock it up...you need pitman arm clearence on right turn maybe to spring..I like to have box back a bit to not lose steering ratio...You will notice in mock up that if pitman arm is striat back then steering wheel will have different number of turns between turning right or left , moot point as all old Fords with cross steer behaved that way, the slower the box ratio the more it shows up...Moving pitman arm two/three teeth to left will correct this...

 

Yeah, it's got stops for it- i'll have to make sure they're adjusted correctly- i've hear that using hitting the end of travel on the steering box is hard on them so stops are needed anyway.

Thanks for the input! i'm hoping to get back underway soon (kinda had a big slow down when i got remarried and had a new baby at 42 years old..

 

I've always wondered this! Why was the pitman off from straight forward to straight back! The shaft has 4 master splines that make you put on the pitman at only 4 different orientations 90* apart.

I figured i could center the box, then remove the mastersplines and orient the pitman straight back- would that not work- or is there some geometric reason they do this?

 

Basically they may done what I am talking about by 61'..Take the masters out and do some experimenting...

 

When I set up a steering box I check clock to clock on the steering box, and then center it at exactly half the rotations. Then mount the pitman arm in the location I want, and make up my drag link to fit with wheels pointed straight forward. It's as simple as that.
I've never seen a setup that the wheels moved far enough to have the pitman arm move much past 45 degrees each way before the wheels hit the stops. Of course you'll always want to check yours, but I'd be surprised if it did have much over 90 degrees travel lock to lock.
My only issue with the stock Falcon box is the column is pressed into the box, and it's a 50 year old box. Replacing it with a newer junkyard box is usually cheaper than an overhaul, and you'll end up with a better, newer, and easier to overhaul box if needed. Additionally, the Falcon box is short, so it's harder to get the drag link low enough to keep it flat, where a later Courier, Ranger, etc. box is so tall that it really brings the pitman arm down low, and directly in line with the far side backing plate.