I rebuilt my manual steering box with all new parts. 16:1 ratio ballnut and screw and a brand new sector shaft, new bearings seals
new suspension bushes and ball joints, new sway bar links and mounts
new idler and pitman
bout 5 years ago
I have no slop. if i turn the wheel inside, the wheels outside turn
i personally think ratio changes are best done in the box rather than via a long pitman arm, a long pitman are makes the steering faster (i.e more wheel turn per inch of steering input) in the just off straight position and i don't think that's good for stability. but i've never successfully come up with a decent explanation for this idea ...which means it might be BS.
in an ideal world you'd want to turn the wheel further to take the car off straight ahead. Stability at speed is a good thing. you don't what a "sneeze and find a ditch" type scenario.
and less turning of the steering wheel as you navigate round the twists is good, minimal input to improve your arc around that tight turn at speed.
Much like a variable rate steering rack, quite dead in the middle, and faster towards the lock (predominantly a japanese Australian and european thing).
i think you get the opposite with a longer pitman arm.
A longer arm might be pretty good for circle track racing. you get the ratio improvement but you are indeed going round a corner for 80% of the time, who cares about straight ahead etc
2 inch pitman arm turned through 2 degrees, short arc scribed by the ball stud end of it
2 mile long pitman arm turned through 2 degrees really long arc scribed by the end of it
steering input in respect to how far you turned the steering wheel is the same
steering input in respect to effort to turn the wheel will be different
hopefully that illustrates what i'm getting at.... don't have the maths/physics/alignment knowledge to back it up

and as i say i might be wrong,
We have had "spirited" discussion here about it before...
Dave