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One thing to consider: do both pitman arms have the same features at both ends so they fit the other pitman shaft and center link? The parts book says they use the same nut to hold on the arm, so that is a good sign. Not Mopar, but related to this line: I once replaced the very worn power steering box (a poor early design and problematic for rebuilds) in my 56 Oldsmobile with a power steering box from a 70 Olds 442. 56 was the first year for the flexible coupling used on GM cars, so none of the steering column was affected. The newer box used the same 3-bolt pattern on the frame and accepted the 56 mounting bolts (for the correct length per frame thickness.) The pitman shaft had the same spline count and size, so I could use the 56 pitman arm. The pitman arm attachment to the center link is totally different, so the 56 arm was mandatory. Result: no more play, the new box required fewer turns for the same steering effect so the steering was faster. The car didn't handle any better since there were no mods to the suspension. Dave Homstad 56 Dodge D500 ------------ On Sat, May 16, 2015 at 10:14 PM, Jim wrote: For the first question, compared to what it was before changing the pitman and idler, it's likely that the steering at low speeds would become heavier but at higher speeds it would feel more responsive and a bit heavier than before. For the second question, compared to what it was before changing the pitman and idler, the main change likely to be felt is that the steering becomes less responsive, i.e. it takes more turning of the steering wheel to get whatever amount of "turning" you want. Because it's power steering the steering effort for the driver will be essentially the same. I'm not sure I understand what you mean by the net results are contrary to each other. What's happening with the change in length of pitman arm (and idler arm to keep the geometry from getting wonky) is that as the pitman shaft turns its turning movement changes into side-to-side movement at the end of the pitman (and idler) arm. So for a 15 degree rotation of the pitman shaft with a short arm you will get perhaps 6 inches of movement (in an arc) at the end of the arm. But if you put a long arm on it and turn it the same 15 degrees you will get greater movement at the end of the arm, proportional to the relative lengths of the arms,.. with an arm twice as long the end of the arm moves twice as much, 12 inches, for the same 15 degrees of shaft turn. That's going to make the front wheels turn left (or right) twice as far as it did with the shorter arm even though it's the same 15 degree turn of the pitman shaft, and the same number of turns of the steering wheel to get that 15 degree shaft turn. It's not quite that simple because the movement at the end of the arm is in an arc, not a straight line, but the principle is the same, you just need to use more geometry to calculate the actual numbers and because it's an arc it becomes less and less side to side movement at extreme angles. But for the relatively small angular movements of the pitman shaft as used in cars it won't be hugely different. And when you make the arm twice as long, giving twice as much end of arm movement for the same angular change of the pitman shaft it means the effort to turn the steering wheel is twice as much. Again, it's going to be pretty much in proportion of the lengths of the arms. So if it took 16 pounds to turn the wheel at 1 mph when parking and you change a 8" arm to a 10" arm, you up the effort by 25% and it will take 20 pounds. I've stuck with the 15 degree shaft turn so it's an apples to apples for the starting point. If you change pitman length (put a longer one on for example) what used to take 15 degrees of shaft turn might only take 10 degrees of pitman turn to go around the same corner, but it will be harder to turn the steering wheel to do it (with manual steering). Most manual steering was around 20:1 so for a 15 degree pitman shaft turn you'd have to turn the steering wheel 20x15 degrees, 300 degrees, nearly a full turn. If you changes pitman arms so it only took 10 degrees, then the steering wheel would only need to be turned 200 degrees, a bit more then half a turn (but with more effort to do so). Jim Delton ___________________________________ From: Neil Vedder <esierraadj@xxxxxxxxxxx> To: L-FORWARDLOOK@xxxxxxxxxxxxx Sent: Saturday, May 16, 2015 4:42 PM Subject: Re: [FWDLK] Pitman arms? So, what would be the net ANTICIPATED steering-effect (feel/input and response) if a MANUAL steering car has its Caster adjustment set at 'zero' (which happens to be where a lot of manual steering Caster adjustments are set at, anyway).....if it has the longer (P/S) Pitman, and Idler Arms??? And, vice-versa: a P/S car gets the shorter MANUAL-steering Pitman and Idler arms (and, some degree of Positive Caster adjustment...which is what Power Steering cars typically have be dialed-into them)?? I think the above is stated correctly, and the net-results are contrary to each other. Neil Vedder ************************************************************* To unsubscribe or set your subscription options,
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