There is a bolt in it that tightens down causing fluid to be tighter per say . And that means stiffer on the wheel .
Not entirely true
These are Saginaw steering boxes, designed in the 60s. What you're actually doing is adjusting the backlash (i.e. tooth clearance); much like setting up a differential gear assembly (Ring/Pinion) after a rebuild/replace/whatever.
The plate under this nut you're loosening is called a 'top plate adjuster.' This nut determines the backlash
between the
power piston teeth (what the steering column/shaft connects to) and the
sector shaft teeth (what the pitman arm connects to), and thus, the return to center characteristics of the steering. By adjusting this, you will be able to get back most of the stock characteristics of the steering. Improperly adjusted, you risk the chance of binding/disengagement of the teeth due to improper backlash.
It's DEFINITELY not something to take lightly, as it
is the steering that we're dealing with, here.
Basically, the sector shaft has tapered teeth (3); wide at the top (closest to the adjuster nut) and narrow at the bottom (closes to the pitman arm.) The power piston teeth are not tapered, but are widely spaced.
When you adjust the allen at the top of the box, you're moving the sector shaft up and/or down, changing the clearances of the tooth mesh, or backlash.
- Too far down, or tight, and you force the sector shaft teeth to power piston teeth, causing binding to occur. This results in an oddly tight steering response, binding, lack of RTC (return to center), and possible breakage of steering components within the box.
- Too far up, or loose, and you increase the sloppiness in steering response, as well as risk possible disengagement of the steering teeth, resulting in no steering control.
These are extreme cases, but I hope it gives you a little more insight as to exactly what you're adjusting..
Since we all love pictures...
The Power Piston gear teeth:
The Sector Shaft teeth (notice the tapering) :