Front End Alignment Specs vs Behavior (Return to Center)

Stanglover said:

Just curious, what brand / make idler arm did you put in there?
The geometry of some repops may not be as the original and if so, that will undoubtedly cause problems. That could be what is causing some of your issue.
Here's a sketch I did to illustrate what I mean. Sorry, this copy is not very clear.
The part I put in my car was the Rare Parts brand (from NPD) and while it may look different the geometry is the same and I have no issues with steering in that regard.

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The new Idler came in a rebuild kit I bought from a member of this forum. I've already thrown away the bag it came in, but its geometry matches what I removed, along with the Steering Arm. It has a PN 3355-A on the arm. The bushing on the Center Link has the same PN as a Moog bushing I have. It looks a lot like the Rare Parts version, but not as beefy.

After reverting back to the old, but still good, Idler, it now returns to center. That Center Link joint was very stiff. Maybe these things break in or maybe the rubber on the one I have has hardened? Also, I put it together dry....maybe it's supposed to get some silicone grease?

Edit: I found a picture from the seller's posting:

basstrix said:

The new Idler came in a rebuild kit I bought from a member of this forum. I've already thrown away the bag it came in, but its geometry matches what I removed, along with the Steering Arm. It has a PN 3355-A on the arm. The bushing on the Center Link has the same PN as a Moog bushing I have. It looks a lot like the Rare Parts version, but not as beefy.

After reverting back to the old, but still good, Idler, it now returns to center. That Center Link joint was very stiff. Maybe these things break in or maybe the rubber on the one I have has hardened? Also, I put it together dry....maybe it's supposed to get some silicone grease?

Edit: I found a picture from the seller's posting:
View attachment 94001

Click to expand...

Thanks for clarifying the part you have. Perhaps you're right, a tight bushing.
Now, I have to eat some "humble pie". I went back over my receipts from NPD and found the one for the idler arm I actually bought in 2015. It was NOT the Rare Parts one as I thought. It was 3355-1 but it too matches the old one I took off and still have. In the listing from NPD, it now mentions the upper bolt hole may need to be slotted upward for some installations. That is what got me rethinking my statement because that's exactly what I had to do. Sorry about that or any confusion I may have caused.
Regardless, the sketch is correct in so much that it illustrates the important dimensions.

Stanglover said:

Thanks for clarifying the part you have. Perhaps you're right, a tight bushing.
Now, I have to eat some "humble pie". I went back over my receipts from NPD and found the one for the idler arm I actually bought in 2015. It was NOT the Rare Parts one as I thought. It was 3355-1 but it too matches the old one I took off and still have. In the listing from NPD, it now mentions the upper bolt hole may need to be slotted upward for some installations. That is what got me rethinking my statement because that's exactly what I had to do. Sorry about that or any confusion I may have caused.
Regardless, the sketch is correct in so much that it illustrates the important dimensions.

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Thanks for the insights. When I was replacing the Idler, I set the two side by side and after install, A quick visual confirmed the Center Link was running horizontally and square to the front-rear axis of the car. The attached diagram is representative of what my car has for Idler/Center Link config. In the 1971 manual, I'm seeing two configs. The alternate config has the Center Link registering on the upper surface of Ilder. In my Vehicle Dynamics coursework, I became familiar with Roll, Pitch, and Yaw axis for vehicles. I use Pitch axis to describe the ideal orientation of the Center Link.

basstrix said:

Thanks for the insights. When I was replacing the Idler, I set the two side by side and after install, A quick visual confirmed the Center Link was running horizontally and square to the front-rear axis of the car. The attached diagram is representative of what my car has for Idler/Center Link config. In the 1971 manual, I'm seeing two configs. The alternate config has the Center Link registering on the upper surface of Ilder. In my Vehicle Dynamics coursework, I became familiar with Roll, Pitch, and Yaw axis for vehicles. I use Pitch axis to describe the ideal orientation of the Center Link.

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That's a very useful diagram. In it "Y" is basically the same as my sketch except it describes the bottom surface of the bushing, whereas I picked the top. In retrospect, the bottom would be more correct as it is the seating surface for the center link.
In my original 1971 Ford manual, I'm not seeing an alternative configuration and in fact the diagrams are poor to say the least and really don't show much at all. The description isn't much better either.
At the end of the day, if it works correctly, that's what counts.

Here's the alternate...says it's for Montego and Torino with power steering...lists some others, as well. There's something similar for other models having manual steering.

Be aware, camber can alters the direction a vehicle follows, but it is also a tire wearing angle. Caster also the direction a vehicle follows. But it is not a tire wearing angle. I prefer to throw caster at a directional stability and tracking issue as compared to using camber (I try to use 0 degrees camber whenever possible).

I ended up with the following, after re-adjusting. I'll drive it a bit and check again.

L Camber: -0.3
L Caster: +3.0

R Camber: -0.2
R Caster +3.0

3mm (1/8") toe in.

Here's an update on the return to center (RTC). I'm experiencing a consistent behavior pattern and wondering if any of you have had similar experience. When I take the car for a drive, when it's been undriven for a while...we'll just say overnight.....the RTC behavior is good, but after driving for just a short distance, the RTC begins to degrade....and after everything is fully warmed up, the wheel practically won't return at all. I've adjusted the Sector Shaft preload and tighter "seems" to make it worse, but even at the original setting (I received at), it still does this (and wanders more)....I have not measured the preload per the service manual procedure, so I don't know how far from ideal the preload is set.

I've thought about it and come up with some root causes.

1. Steering Box Issue (this is remanufactured box bought from NAPA back in the late 80's. I would guess it has less than 20k miles on it.)

2. Limited Slip rear differential is tighter when cold and helping to straighten the the front wheels. I say this because I get a little bit of chatter when I back out of the driveway, making the 90 deg turn to the street....the chatter goes away after the 2nd turn leaving my neighborhood, but it could still be loosening as it warms up.

3. The tires are warming up and have more bite/traction due to incorrect setup specs??? This seems far fetched, so just throwing it out there.

If you've had any experience with this scenario, I'd like to hear from you.

Shop manual specs
Caster -1• to +1•
Camber 0• to +1 1/2•
Toe. 1/16” to 5/16”
These specs worked okay for narrower bias ply tires and provided effortless steering but certainly wasn’t the best for aggressive handling.
Your specs should work well with wider radial tires and should increase steering effort and should return to center easily.
Providing the mechanical linkage moves freely without any binding then that would lead me to the steering gear. If you remove the play from your steering gear at the center position then you may have binding issues off center. With the pitman arm connected to the drag link you probably won’t feel it if there is binding. Worn sector shaft bearings will cause play and tightening the adjustment screw to remove the play will definitely cause binding. If binding is not the issue, then possibly fluid contamination and or valving issues may be a problem. Check the fluid for contamination and burnt smell.
I may or may not be on the right track for you, but based on what you stated, this is how I would go about it. I hope this helps.

@cjstaci The fluid is clean and clear...I don't suspect any issues there. The gear box has end play and I have adjusted sector shaft in an attempt to reduce the play....it "seems" to make the RTC situation worse....but if it does make it worse, it's subtle.

Is there a go-to shop to get these boxes rebuilt? Any idea what I can expect to pay to get one rebuilt? When I was looking for the flare fitting seat that presses into the box, I talked to a guy who does rebuilds...thinking I may give him a call to see if he's heard of this happening.

There has been many posts on PS boxes. I have posted on my rebuild experience, but I'm far from being an expert. I was fortunate to have a machine shop where I could repair and rebuild the sector shaft and other parts.
You cannot properly adjust the sector shaft preload with the box in the car. Early on, I tried that and almost ditched the car! If you do attempt that, no more than a 1/4 turn clockwise on the hex screw. If there is too much free play at the steering wheel, more than 1" either way, then the ONLY way to fix that is to replace the balls inside the box. Ford used to offer rebuild ball kits in 6 sizes and to 5 decimals tolerance. Very precise in other words. Replacement balls can be bought to 4 decimals from bearing specialist companies, but expect to pay 2-3 dollars apiece and you need 24 in a V/R box, 22 in a standard ratio.
Your best bet might be to buy new or rebuilt from RedHat for example. Many here have had good luck with them. Lares also has been recommended.

Stanglover said:

There has been many posts on PS boxes. I have posted on my rebuild experience, but I'm far from being an expert. I was fortunate to have a machine shop where I could repair and rebuild the sector shaft and other parts.
You cannot properly adjust the sector shaft preload with the box in the car. Early on, I tried that and almost ditched the car! If you do attempt that, no more than a 1/4 turn clockwise on the hex screw. If there is too much free play at the steering wheel, more than 1" either way, then the ONLY way to fix that is to replace the balls inside the box. Ford used to offer rebuild ball kits in 6 sizes and to 5 decimals tolerance. Very precise in other words. Replacement balls can be bought to 4 decimals from bearing specialist companies, but expect to pay 2-3 dollars apiece and you need 24 in a V/R box, 22 in a standard ratio.
Your best bet might be to buy new or rebuilt from RedHat for example. Many here have had good luck with them. Lares also has been recommended.

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What is the risk of going beyond 1/4 turn CW with the sector shaft adjuster? I went to 1 full turn CW, in 1/4 turn increments and then went 1/4 CCW from the initial position as received from NAPA.

The procedure in the Ford Service Manual for measuring preload is performed with the box installed. It calls for the Pitman Arm to be removed, Steering Wheel cover removed (to access nut), and Power Steering Pressure Line removed. You're the 2nd person to say it needs to be done with box removed, so there must be something to that?

I haven’t had to replace my mustang steering gear, but I did replace the one in my 81 F350. I bought it from Redhead in Auburn Wa. I lived in the area at the time so it was easy to pick up and exchange the core. It has worked perfectly so far and I have driven it approximately 20,000 miles.
One thing I would say is most of us drive late model vehicles every day and most late model vehicles have a lot of caster designed into them. Also rack and pinion steering, electric assist and even monitored by the computer. They practically drive themselves, and some cars do. Our old cars require more driver input and feel a little sluggish in comparison. Not saying the old cars are bad, it’s just that when you get used driving late model cars, it usually leaves you wanting more from the older cars.
When I rebuilt the suspension, I shimmed the upper A-arm to get more caster. I was able to get 4 degrees. I also have a 1-1/8” sway bar, stiffer springs and Viking double adjustable shocks. The car handles fairly well considering it has a nose heavy big block. It stays flat in the corners and overall feels good, but no where close to the way my 22 GT handles.

basstrix said:

What is the risk of going beyond 1/4 turn CW with the sector shaft adjuster? I went to 1 full turn CW, in 1/4 turn increments and then went 1/4 CCW from the initial position as received from NAPA.

The procedure in the Ford Service Manual for measuring preload is performed with the box installed. It calls for the Pitman Arm to be removed, Steering Wheel cover removed (to access nut), and Power Steering Pressure Line removed. You're the 2nd person to say it needs to be done with box removed, so there must be something to that?

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As you probably know, the teeth on the sector shaft are tapered as are the teeth on the rack piston. The more the sector shaft is screwed downward into the rack piston teeth, the tighter the movement will be, if that makes sense.
I reread the passage in the manual and you are correct, it can be done that way. The important part is remove some of the fluid so the action of turning the s/wheel won't build pressure and throw off the reading. 6in/ lbs is very little. Total preload including the input shaft, should not exceed 8 in/lbs. I guess from my own experience, the box was on the bench anyway. There is one item in the manual that sounds easy, but will need a good impact wrench and puller to remove the pitman arm. Those suckers are on tight!!