Pitman arm installation

[Solid]

Does anyone know if the pitman arm is splined so that it can only be installed in one place? My memory is that is the case.

[action]

Generally - yes

Action

[action]

The Pitman arm is splined.
Usually there is a flat spot in the splines or an extra wide spline that requires the arm to be installed on the sector shaft in one way only.

Action

[Solid]

Ok that was my memory too. So since it is not possible to install it offset, can anyone think of a simple reason why a car that aligns just fine would have more travel when turning right than left? My guess was that the pitman arm was 90 degrees off but since that doesn't seem to be possible, and there is nowhere near that much adjustment range in the tie rod ends, I can only think there is something internal to the steering gear that can be improperly assembled during a rebuild.

[TonyC]

Yes, the Pitman arm is designed to go onto the sector shaft only one way, so nobody could make that kind of mistake, even if they were stupid enough to do so. That symptom sounds like an internal fault with the steering gearbox; since alignment and linkage have been ruled out as suspects (and I presume the rest of the suspension/steering components), it would have to be the steering gearbox itself that causes more turns in one direction than the other. Properly assembled and calibrated, the gearbox turns should be equal in either direction.

OR...if the original pillow spacers (or "insulators," in FoMoCo lexicon of the day) are still in place, maybe they could be the culprit. They cause the gearbox to twist at odd angles it was never meant to; and when they wear and tear, as they all do, that will cause the gearbox to twist even more prominently, causing handling/control problems and causing chain-reaction wear on the rest of the steering system.

Focus your attention on the gearbox and the spacers (if you haven't changed them to the all-metal variants now on the market); one or the other (or possibly both) has to be the cause of the problem.

---Tony

[Solid]

Yes, the Pitman arm is designed to go onto the sector shaft only one way, so nobody could make that kind of mistake, even if they were stupid enough to do so. That symptom sounds like an internal fault with the steering gearbox; since alignment and linkage have been ruled out as suspects (and I presume the rest of the suspension/steering components), it would have to be the steering gearbox itself that causes more turns in one direction than the other. Properly assembled and calibrated, the gearbox turns should be equal in either direction.

OR...if the original pillow spacers (or "insulators," in FoMoCo lexicon of the day) are still in place, maybe they could be the culprit. They cause the gearbox to twist at odd angles it was never meant to; and when they wear and tear, as they all do, that will cause the gearbox to twist even more prominently, causing handling/control problems and causing chain-reaction wear on the rest of the steering system.

Focus your attention on the gearbox and the spacers (if you haven't changed them to the all-metal variants now on the market); one or the other (or possibly both) has to be the cause of the problem.

---Tony

I had the box rebuilt years ago but I can't remember if it was Baker's or Lincolnland anymore. I only noticed recently that it has far more travel to lock to the right than to the left, but it has probably been that way for years without me noticing. Now that I do, it's pretty annoying to have a much tighter turning radius to the right than to the left (it makes U turns impossible on most surface streets unless there is a driveway entrance to cheat into).

'61-62 don't have the spacers. I probably should get a rebuild kit and pull the steering gear to figure out what the assembly error is. I'm going to assume that it is possible to install the sector shaft offset.

[mikemm]

How much is it off by ?

[Solid]

I had time to mess with this issue yesterday. What a pain in the ass it ended up being just to remove the pitman arm to look at the splines clearly, but I did get some answers.

First, the original pitman arm and splines are designed to allow installation at 90 degree increments not just in one orientation. The factory service manual says to rotate all the way to one side the. Turn back “about two turns” and then install the arm. I found in testing that with the pitman arm removed, the steering gear will go about 3.8 turns lock to lock, so it seems that Ford anticipated a situation in which the car had some bias in turning radius from left to right.

What caught me a bit by surprise was that with the pitman arm installed after performing this about two turns approach, the steering wheel was still centered and with the arm installed there are only three turns lock to lock. Some travel is being lost here, and after putting everything together and driving it a bit, I think I know what might be happening. It could be that I need to go one 90 degree land over and then just pull and re-center the steering wheel, but I also found it impossible to get the pitman arm puller into place without unhooking the exhaust. I wonder if my down pipe on that side might be limiting the range of travel for the pitman arm. I won’t be able to look at it again for a few weeks.

I've edited this to add some photos that show the splines allow 90 degree installation increments.

[TonyC]

Wow, I didn't know that! Well, then, I can see that being a bit of a complication! Frankenstein's Pitman arm is not designed that way; that tells me the engineers saw a problem with the original '61 design and altered it in later years so it could go on only one way, as opposed to four.

That changes the way I would diagnose the problem, then. You may be on the right track, suspecting the arm is off by 90º. If your guess is right and you end up curing the problem, that should be part of record for all other '61 owners who may have to remove their Pitman arms. I wonder how many subsequent years may have had that issue before the engineers finally got wise?

---Tony

[Solid]

FWIW mine is a '62 but I don't think the gearbox internals are really very different for the later years, I think they just changed the center link a bit to accommodate the geometry change from the later addition of the spacers. Looking carefully at the photo that Action posted, that one looks like it has 90 degree increments too, so maybe it is comms in the design of these. I haven't owned another car with a steering gear vs a rack in forever and the last was a first gen RX-7 for which I don't really remember the details of the steering system. On my car at least, when I have very carefully dialed the steering gear to the middle of its range ~1.8 turns, then slide on the pitman arm, the center link end of the pitman arm doesn't quite line up with the center link stud when the steering is set dead ahead. So... I am willing to bet that every Lincoln actually has a small difference in how tightly it can turn left vs right depending on which way the installer chose to turn the steering gear in order to get the pitman arm onto the center link.

I will be interested to see if the downpipe is what is limiting my range to the left when I get back to the car in a few weeks. It is the only reasonable explanation I can think of for why the steering gear goes from 3.8 turns lock to lock to 3.0 turns after connecting the pitman arm.

[TonyC]

Hmm. Well, I know for a fact that the design was altered later on. From '65 on, the splines on both the sector shaft and the Pitman arm had only one of those larger grooves, to ensure that the installation could only go on one way. Maybe '65 was the first year the engineers addressed that issue; it wouldn't be the only time it took them years to determine that an original design concept wasn't as good as they expected it to be.

---Tony