AVAILABLE POWER STEERING RATIOS 
 

There are two types of power steering gears, constant ratio and variable ratio. Variable ratio was available, starting in 1969 and offered well into the late 70's. Constant ratio was used before and after the 70's

Constant ratio is felt to be more predictable for the driver in a racing type application, however varable ratio is less twitchy in a straight line, BUT the 69 variable ratio boxes were very fast average ratios, and has low effort levels which can make the car a bit twitchy feeling to some drivers.

Two ways of listing ratios: OVERALL RATIO - measured at the wheel, and BOX RATIO - measured at the steering box output shaft.

VARIABLE RATIOS- Two numbers, first number is the center of travel ratio, the second is ratio near the end of travel, measured at box output shaft, not the wheels. the boxes below were used by GM in the 70's only the ratios marked * are First Gen boxes.
  • 14-11:5:1
  • 16-12.4:1 *
  • 20-16:1
CONSTANT RATIOS- I believe these are at the box ratios, not overall.
  • 17.5:1 *
  • 14.4:1
  • 12.7:1

NOTE: the ratio numbers change a bit from article to article.  12 to 1, 12.4 to 1, and 12.7 - to 1 they are all talking about the same ratio, and 12.7 is more correct according to what my box measures.

The steering linkage adds an additional multiplier to the basic box ratio to arrive at an overall ratio. It could be a positive or negative multiplier (number less than one - a decimal).

Pitman arm long - 5.8", short- 5.25" These measurements are fairly accurate.

Outer steering arms - short 5.25", medium 5.75", long outer steering arm, is roughly 6.2" long. These are pretty close, I may revise by 1/8" + -

The factory sales brochure for 1967 shows power steering ratios of 17.5, to 1, - the "fast steering"15.6 to 1.

GM OPTION CODES


N40 = Power steering option

N44 = Fast ratio option (could be ordered on manual or power steering)

On Z/28 only, got a "special fast ratio" MANUAL STEERING option that was faster than normal N44 fast ratio.

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