Pitman arm positiin

[hunter1]

Can someone check the position of their pitman arm when the steering box is centered and possibly take a picture of it in relation to the frame rail? With my box centered (5.8 turn box), my pitman is positioned about 14 degrees outboard of the frame rail. I was thinking it should be more centered with the frame rail, but maybe I’m wrong again. I’m installing a tie rod over linkage and need to position my saddle for welding and just seems too far away from the knuckle in the centered position.
Thanks ahead of time!

 

[rocknhorse76]

With the box centered, the pitman arm should sit parallel to the frame rail.

 

[hunter1]

That’s what I thought. I need to see if this box is for something else and was just used in place of a Bronco ps box?

 

[SteveL]

If I remember right both of mine aim a little to the outside of the frame. That's with the 4 turn 4x4x2 boxes

 

[rocknhorse76]

That’s what I thought. I need to see if this box is for something else and was just used in place of a Bronco ps box?

Are you using a keyed pitman arm (has one bigger spline that prevents you from aiming the arm where you want it)? If so, you can either file that key down, or buy an arm that isn’t keyed. Center the box, install the arm where you want it, and then set the saddle location.

 

[hunter1]

This is the position of the pitman arm with the box centered. This is the pitman arm with the four solid splines for clocking. It’s a ford arm, so I would assume the box was something used on fords from the era.

 

[Oldtimer]

This a stock C8TA-3590-F Bronco pitman arm, and keys in yours are clocked about the same.



Bronco box is uniqe.
A side view of mounting pads would confirm it is a stock box boted to stock holes in frame.

 

[hunter1]

Must be a stock Bronco box then. I removed from another Bronco I have, and it bolted up to this frame without modification.

 

[hunter1]

Is there any way to get the box out of time if it has been apart in the past?

 

[rocknhorse76]

That’s right, I forgot they had 4 keys. Does the box turn an equal number of turns in each direction?

 

[hunter1]

Yes, so probably not out of time. I think I’m going to cut the wide splines down with a die grinder and position it parallel to the frame.

 

[jamesroney]

With the box centered, the pitman arm should sit parallel to the frame rail.

This is an interesting statement.

"The pitman arm should sit parallel to the frame rail." I suppose there are reasons why that might be true. But the early bronco is kind of unique in that the pitman arm actually sits outboard of the frame by about 1 "notch." I think it is because they wanted the drag link to be as long as possible. But it has always looked strange when the steering box is properly centered in its range of motion, and the pitman arm hangs out to the side.

There is no reason why the pitman arm needs to point parallel to the frame. And many of the dropped pitman arms are not keyed...so you can put them on in the "wrong" place without issue.

But @hunter1 yes, the factory Bronco pitman arm sits about 10 degrees off center when centered.

 

[Viperwolf1]

Is there any way to get the box out of time if it has been apart in the past?

Not if it has stock parts in it. It only goes together one way.

There are different end caps and piston spacers used inside some other Saginaw boxes that limit the piston travel, but they don't affect steering ratio or the center position. Those spacers can make a 6 turn box seem like a 5 turn box, but it won't turn any faster.

 

[ba123]

Yeah, I was unsure of this as well when I reassembled mine after a multi-decade sit. I tried to install mine parallel and it was clearly not right.

Ended up being slightly outside of frame to get it right.

 

[DirtDonk]

If I’m not mistaken, the early bronco boxes were, as stated, off by one spline, or 10° to the driver side.
At some point in production, possibly 74, they changed that orientation and the Pitman Arm pointed straighter down the frame.
It would’ve seemed logical to have changed it in 76, when they also changed the entire linkage design. But I seem to remember seeing some 73s, and all of the later ones that I looked at, pointing straight back.

If we can find some Pitman arms with later engineering codes on them, this might pinpoint the change. Or perhaps the change from the six turn to four turn 4 1/2 turn boxes was when the change occurred.

Have you worked on any later Broncos James? Seems like you were talking about a 77 recently.

 

[Viperwolf1]

At some point in production, possibly 74, they changed that orientation and the Pitman Arm pointed straighter down the frame.
It would’ve seemed logical to have changed it in 76, when they also changed the entire linkage design. But I seem to remember seeing some 73s, and all of the later ones that I looked at, pointing straight back.

If we can find some Pitman arms with later engineering codes on them, this might pinpoint the change. Or perhaps the change from the six turn to four turn 4 1/2 turn boxes was when the change occurred.

Have you worked on any later Broncos James? Seems like you were talking about a 77 recently.

I've never seen any evidence of this and I've probably been inside more Bronco boxes than anyone I know. The keys on the sector shaft are aligned to the orientation of the case on all of them. You can just look at the splines and know if the shaft is centered so it can be removed. If there was ever any change, it would be in the spline alignment of the pitman arm. I've also never seen a stock Bronco PS pitman arm with anything different than the original '73 engineering number.

 

[DirtDonk]

Good to know. Thanks Phil.
I was thinking more along the lines that it was the arms that changed, rather than the sector shafts.
I questioned whether there was a change in the boxes or not. It seemed that something changed at any rate. And more likely it would’ve been the arms.

But wouldn’t there be a separate number for the 76 and 77 arms anyway? They have the smaller tapered hole versus the 73 through 75.
Maybe that goes back to the changeover to power steering in 73 anyway. If they have a 73 engineering number, are those the ones that point straight back along the frame?

If not, then perhaps it was only the manual steering arms that were 10° off, versus the power steering arms.
Inquiring minds need to know…

 

[ba123]

I can't comment on stock stuff since the only stock part is my 76 box. My pitman arm and everything else is from Bulleteproof, but I think there was a box change on the 76-77, but I sometimes have no idea if I know what I'm talking about. Maybe they just changed the internals to make it 4-turn? Which brings up another question...Mine seems to be a 3.25 turn and I don't know why. It's a stock '76 box so either I did something to it other than seals years ago and don't remember, or there's something weird going on.

And I guess that just because I have my 76 non-stock arm outside the frame, doesn't mean the stock one was.

And I could make it parallel with the frame if all I did was slightly shorten my tie rod, anyway, since my pitman arm is not keyed.

So, I guess that was zero help?

 

[jamesroney]

I've never seen any evidence of this and I've probably been inside more Bronco boxes than anyone I know. The keys on the sector shaft are aligned to the orientation of the case on all of them. You can just look at the splines and know if the shaft is centered so it can be removed. If there was ever any change, it would be in the spline alignment of the pitman arm. I've also never seen a stock Bronco PS pitman arm with anything different than the original '73 engineering number.

Hi @DirtDonk I'm halfway with @Viperwolf1 on this. Every sector I've seen is square to the box, and the key offset is in the pitman arm. (or clocked 45 degrees...but yeah)

But I am unsure on the pitman arm. I cannot use the engineering number to make that determination about the finished part. That engineering number is the raw casting number, and will be on the BOM for the finished part. If someone has a MPC, they will be able to tell if the PART number changed in 77. I know that the part number changed between 73 and 77 because of the inverted Y, and the machined taper changed. I do not know if the pitman spline alignment changed. Since both features are machined after forging, they would likely all carry the same engineering number.

I don't have a good 77 pitman arm to look at here. So I'm basically useless.

Gotta go...

 

[Oldtimer]

Power Steering Pitman Arm
72------D3TZ 3590-A
73/75--D3TZ 3590-A
76/77--D6TZ 3590-B

Note:
The 6 turn PS box @jamesroney loaned me came with a pitman arm with casting # C8TA-3590-F.
It is entirely possible that power steering pitman arms from 72 thru 77 all used the 68 manual steering pitman arm casting with different spline broaching and tie rod end tapered hole reaming. I don't think there is a snow balls chance that anyone has copies of part number drawings.
The stock pitman arm on my 68 Bronco is broached with NO indexing splines, and can be placed at any angle on steering box.
EDIT:
Casting number is same as others.
Also, as shown in below photo, 68 pitman arm has punch marks that correspond to wide splines in later year arms.