Rebuilding Saginaw power steering box

[Stanglover]

@ Bentworker

I was not able to locate your thread on rebuilding and or converting a Saginaw power steering box, but I have questions I'm sure you could answer for me.

Currently, I have an SPA-T variable ratio box in the car, a 71 Mach1. I had this rebuilt by an "Expert" (and I say that with reservation) and I won't go into all the details here. In short, the rotational valve was bad, no power on right turns and he didn't replace it. I got a SPA-T box from OMS for parts, took it back to the clown as I didn't want to screw it up. Well guess what he screwed it up and I re-did it myself. It's in the car and working fine albeit with a bit too much s/wheel play than I'd like. In the interim, I picked up a SPA-S fixed ratio box that was working and have had that in the car for most of last year. I just replaced the "T" box yesterday, so I thought Id like to put a back-up "T" box together from the best of parts from the 2 I have.

Ok finally the questions;

 1/ One casting, the "T" box from OMS, I think is shot, the ware marks from the Teflon rings on the rotational valve are deep and irregular. Can they be honed or hard chromed or otherwise repaired? The "S" box casting look much better and likely what I'll use.

 2/ the rotational valve from the S box is good, but is the torsion bar the same as in the T box? It did feel easier to turn the wheels, so I wondered.

 3/ Number of balls; I know there are 24 in the v/ratio box and I only had 22 in the fixed ratio, 11 of each. If I had an odd number I would know there was some missing. Is this correct?

4/ From my playing around, I came to the conclusion that the only real way to remove free-play is to change the ball diameter to a larger size. Are these available and from where? Just tightening the sector shaft preload or the input shaft preload is not the answer.

Any help or suggestion are most welcome. PM me if you prefer. Sending a box to the US for rebuilding is not a good option for us in Canada right now, but there is a company in the Toronto area I may contact. I'd like to do it myself if possible though.

Thanks,

Geoff.

 

[Don C]

Here you are

https://www.7173mustangs.com/thread-playing-with-steering-boxes-spa-s-fixed-ratio-spa-af-variable-ratio-firebird-12-7

This should be in a tutorial...

 

[Stanglover]

Here you are

https://www.7173mustangs.com/thread-playing-with-steering-boxes-spa-s-fixed-ratio-spa-af-variable-ratio-firebird-12-7

This should be in a tutorial...

 Wow Don. You da man!! Obviously your search skills are far better than mine. That's the one I was thinking about, but couldn't remember the full title.

Thank you,

Geoff.

 

[Bentworker]

1). I would use whatever casting is in the best shape, they are cast iron and with how plentiful the boxes are I doubt it would be worth the cost to bore and sleeve. I have taken a ball hone to some, but of the grooves are deep I’d just find another casting.

2). I measured a fixed and a variable box T-bar and the numbers are somewhere in the giant thread Don posted the link to. The fixed ratio box was slightly smaller.

3). I have seen 24 balls in every one I have fooled with, the ball screws are a difffrent pitch so anything is possible by design or with someone dropping parts on the floor in years past.

4). I don’t know where to source different balls. I have always treated the ball screw, piston and balls as one matched assembly. If you don’t like what you have maybe it is time to go get a 12.7:1 assembly out of a wrecking yard. What I am saying is if it seems to be worn find another. Currently there seems to be an unlimited supply of Jeep Grand Cherokees in the yards local to me. Also, some play is normal. Your steering wheel is not directly connected to the ballscrew. It is connected by the t-bar, and by design that has to deflect a few degrees to make the valve port oil one way or the other. With the car off you will be able to move the steering wheel a bit in both directions without the output shaft doing a thing.

If I were you I’d go for broke and find a 12.7:1 assembly to swap in. There are self service wrecking yards up there right? I also have a stash and could part with one if needed. It would fit in a medium USPS flat rate box.

 

[Stanglover]

1). I would use whatever casting is in the best shape, they are cast iron and with how plentiful the boxes are I doubt it would be worth the cost to bore and sleeve.  I have taken a ball hone to some, but of the grooves are deep I’d just find another casting.

2). I measured a fixed and a variable box T-bar and the numbers are somewhere in the giant thread Don posted the link to.  The fixed ratio box was slightly smaller.

3). I have seen 24 balls in every one I have fooled with, the ball screws are a difffrent pitch so anything is possible by design or with someone dropping parts on the floor in years past.  

4).  I don’t know where to source different balls.  I have always treated the ball screw, piston and balls as one matched assembly.  If you don’t like what you have maybe it is time to go get a 12.7:1 assembly out of a wrecking yard.  What I am saying is if it seems to be worn find another.  Currently there seems to be an unlimited supply of Jeep Grand Cherokees in the yards local to me.  Also, some play is normal.  Your steering wheel is not directly connected to the ballscrew. It is connected by the t-bar, and by design that has to deflect a few degrees to make the valve port oil one way or the other.  With the car off you will be able to move the steering wheel a bit in both directions without the output shaft doing a thing.

If I were you I’d go for broke and find a 12.7:1 assembly to swap in.  There are self service wrecking yards up there right?  I also have a stash and could part with one if needed.  It would fit in a medium USPS flat rate box.

 Thank you Bentworker,

 The casting I just disassembled has very little ware, far less than the one I just put in the car, so I'm good with that. Honestly, I don't think this box has ever been apart judging by how much rust and corrosion there was around the end cap clip ring and the jamb nut on the input shaft bearing assembly, but yes, I was curious about the 22 balls bit. If 2 are missing it just happens to be one of each size.

As for the T bar size, if the S box is smaller, can I change the one from the pouched T box?

I had definitely thought about going to 12.7:1 and yes I'd be interested in talking to you more on that in a PM.

 My local yard has several boxes on the shelf, but NONE of them have tags or written ID so who knows what they are! I also looked at several in the yard and likewise, could not find any with tags. Time for another junk yard I'm thinking!

As far as the ball sizes, my 1971 Ford manual list several sizes and describes the process, but as you say no one seems to know where they can be obtained these days. I have a friend who works for GM as an engineer. He is building a resto-mod Mach 1. Because he works for GM, he was able to have a PS box rebuilt at the factory that services the Saginaw boxes, but they would not even talk to me about parts or even rebuilding mine.

I do of course realize that these aren't rack and pinion, so yes some play is expected, but the less the better.

I'll do some more research on the ball situation.

Again thanks for you time to respond,

Geoff.

 

[Stanglover]

Had another thought about the sector shaft, These tend to get chewed up around the bottom seals, so either finding one that is still in good enough condition to use or getting one that has already been hard chromed and reground is a possible problem. I can do the regrind myself, but I'm still looking at a hundred bucks for hard chroming here in Canada. As you know a bad seal here means leaks, don't want leaks!.

What are your thoughts?

Geoff.

 

[Bentworker]

Bad parts go in the round bin.

The sector shaft is interchangeable with the ones used in the GM and Jeep Saginaw 800s. Just make sure you get a variable ratio one for a variable box and vise versa.

 

[Stanglover]

Bad parts go in the round bin.

The sector shaft is interchangeable with the ones used in the GM and Jeep Saginaw 800s.  Just make sure you get a variable ratio one for a variable box and vise versa.

Thanks and yes, I understand that much. It was more about finding a correct sector shaft that doesn't need to be hard chromed and ground, i.e. repaired.

This is more about having a spare ready to go rather than making another change, but having said that, if I can get a fast ratio box built, I'll change it in a heart beat.

Again thanks for your input and past posts on what you did.

Geoff.