The return to center problem probably isn't entirely the box.  2.4 degrees of positive caster is not enough.  You need 3-3.5 degrees.  That's your return to center issue.  It may be hard to get that much positive caster unless you've done the Shelby/Arning drop, which also relocates the upper A-arms rearward i addition to lowering them.  

I highly doubt loosening the lash adjustment will fix it, unless it was set wrong at the factory, which I consider unlikely.  The factory has the correct tools to set the lash, yet they want you to try and do it by trial and error?  Look at an exploded view of the steering gear and you'll also see why adjusting that lash screw isn't likely to address the cause of your issue.  

If the box is really the issue I would send it back to Borgesson and get a replacement.  They may want yours back, and this is another reason why I wouldn't go messing with the lash screw.  What they told you on the phone will be conveniently forgotten, and they'll turn it into your fault.  

Power steering in general requires more caster and the target recommended by Borgeson is in the 4 to 5 range.  I'm running about 4.8 degrees and the return to center on my original V1 box in my 66 is very good.  Shoot for the middle of the 4 to 5 range.  The numb return to center condition has been discussed since the Borgeson boxes were introduced.  Try some google searches on recommended caster for Borgeson box in 67 Mustang.

I do find info online about centering issues, but most of what I find is old information.  I don't see a clear, common solution.  Some say more caster helps, some not so much. 

What's odd to me is that in any other car if I nudge the steering wheel one direction while stopped, it will at least partially return which I believe is just the system unloading stress, like any flex in the hard parts, bushings and tires.  This setup doesn't do that.

I've checked the fluid level multiple times and it's clear and I don't see bubbles.  I'm using a Walmart standard type power steering fluid.  

Maybe disconnect everything from the steering box and see how hard it is to turn with nothing connected. There has to be some kind of break away number it takes to turn one.  Kind of like setting a pinion preload.

When I put the new steering together, I counted the turns on all four tie rod ends so they were the same.  Then I adjusted the toe by turning each adjuster the same amount.  It was in spec when I had it aligned.  He may have biased the adjustment to account for wheel straightening a bit, but it's pretty close to centered.  

I did disconnect everything and checked all moving joints.  The spindles turn very free.  The idler arm had a little more resistance than I thought it should, so I loosened it up a bit.  I think the rubber bushing where the drag link hooks up will be more resistance than the pivot.  The wheel still has a dead feel with nothing hooked to the pitman arm.

I'm using the Borgeson pump.  I'm not sure pressure would impact return to center as much as the amount of assist.  I don't have a good way to check it.

I'm currently putting a new flywheel in the car to hopefully address a vibration but hopefully get to drive it again this week if there is a day that it isn't raining.

It has to be in the box itself.  Nothing else would make sense.

I have the plastic bushing at the bottom of the steering column tube.

I think it's in the box, but considering it seems my situation isn't unique, what's my solution?  I'm willing to bet if I send the box back, they will say it's fine.  I like the advantages of this setup, but I can't see how people would be recommending it if they all drove like mine.

RTM wrote:

Dennis wrote:

I have the plastic bushing at the bottom of the steering column tube.

I think it's in the box, but considering it seems my situation isn't unique, what's my solution?  I'm willing to bet if I send the box back, they will say it's fine.  I like the advantages of this setup, but I can't see how people would be recommending it if they all drove like mine.

 
Have you called the manufacturer yet to discuss the issue and or a solution?

They suggested loosening the adjuster 1/4 turn, but that didn't make a difference.  
 

TKOPerformance wrote:

First, get the Mustang Steve lower column bearing.  That plastic thing is Mickey Mouse a-f.

Second, how long ago did you purchase the system?  

I bought the system in June, and installed in September.
 

BobE wrote:

Realizing that pressure may not be the problem, I would verify with Borgeson what is the proper pressure for your setup. 
If the need be, Borgeson offers a PS pump 899001 shim kit, it allows for adjusting the pressure from 700-1,350 PSI using combinations of the 5 shims included in the kit, and costs about $20. 

Do they sell an inline pressure gauge adapter?
 

Dennis wrote:

BobE wrote:

Realizing that pressure may not be the problem, I would verify with Borgeson what is the proper pressure for your setup. 
If the need be, Borgeson offers a PS pump 899001 shim kit, it allows for adjusting the pressure from 700-1,350 PSI using combinations of the 5 shims included in the kit, and costs about $20. 

Do they sell an inline pressure gauge adapter?
 

 
There are options at there.   I had looked into them.  I thought my saginal pump would have to much pressure for my power rack.  Well it did on paper but after running the pressure through the hydro boost everything feels great and no blown seals yet.