Steering Gear (Power Steering)


Typical steering gear adjustment points.

There are normally three adjustments to be made on standard steering gear. Two of these (worm shaft bearing preload and sector gear lash) are made from the outside of the gear housing, and one (sector gear/shaft end play) can only be checked with the sector gear removed from the unit.

An exploded view of a recirculating ball nut steering gear; these parts are normally disassembled during a steering gear overhaul. Courtesy of Ford Motor Company. These adjustments are normally made in the following order when rebuilding a steering gear (1) sector gear end play - as the sector gear is removed or installed, (2) worm shaft bearing preload - as the worm shaft and bearings are being installed into the gear housing, and (3) sector gear lash - after the steering gear has been replaced.
When adjusting sector gear preload/gear lash, the steering shaft preload must be measured in a 90° portion of the center of the shaft travel; turning the adjuster screw (an Allen wrench) inward will increase the preload. Courtesy of General Motors Corporation, Service Technology Group.

If these adjustments are made with the gear in the car, the Pitman arm must be disconnected. A careful check of turning feel of the gear set should also be made to ensure that the interval gears and bearings are in good shape. Check a service manual for the adjustment procedure and the specifications for a particular car.

Measuring Sector Shaft End Play

To measure sector shaft gear end play, you should:

  • Remove the sector gear/shaft and adjuster screw from the cover by turning the sector gear adjusting screw all the way inward.
  • Try to slide a 0.002-inch (0.05-mm) feeler gauge between the head of the adjuster screw and the bottom of the slot; it should not enter. If it does not enter and the screw rotates freely, no change is required. If the clearance is greater than 0.002 inch, a thicker shim is required. A thinner shim is required if the screw does not rotate freely.
If the clearance between the sector gear and adjusting screws is excessive, the gear might drop too far and cause binding. Courtesy of Ford Motor Company.

Adjusting Worm Shaft Bearing Preload

To measure and adjust worm shaft bearing preload, you should:

  • Select the smallest 12-point socket that will slide over the splines of the worm shaft, and with a low reading, inch-pound torque wrench, measure the torque required to turn the worm shaft.
  • Note that if the steering gear is assembled, the sector lash adjuster should be turned completely out or up to eliminate any possible drag between the two gears. If an excessive amount of slippage occurs between the socket and the shaft splines, a tighter fit can be obtained by wrapping a strip of cardboard around the shaft and forcing the socket over the shaft and cardboard.
  • Obtain the worn shaft bearing preload specification and compare it to your readings. If specifications are not available, a rule of thumb is 5 inch-pounds (0.5 N?m) of torque.
As a general rule, the average person can turn a worm shaft with a thumb and forefinger and notice a definite turning resistance.
  • If an adjustment is required, loosen the lock nut for the adjuster plug and rotate the adjuster plug inward to increase preload or outward to reduce it. When the effort to turn the worm shaft matches the specifications, tighten the adjuster lock nut and double check the preload to ensure that it has not changed.

Adjusting Sector Gear Lash

To measure and adjust gear lash, you should:

  • Rotate the steering shaft one direction until it stops. Next, rotate it the opposite way, counting the number of turns it takes to reach the other stop; divide this distance by two to determine the center of travel for the steering gear.
  • Turn the shaft one turn from either end stop and, using a low-reading, inch-pound torque wrench, measure the steering shaft preload. Record this measurement.
  • Turn the steering shaft to the centermost position, and remeasure the steering shaft preload. The difference between these two measurements is the sector gear lash measurement.
  • Obtain the sector gear lash specifications and compare them to your measurements. If specifications are not available, a rule of thumb is 10 inch-pounds (1 N?m) total or 5 inch-pounds (0.5 N?m) greater than the amount of steering shaft bearing preload.
As a general rule, the average person must use both thumbs and forefingers to exert 10 inch-pounds of torque and rotate the steering shaft as it passes through the center of travel.
  • If an adjustment is required, loosen the adjuster lock nut and turn the adjuster screw inward to increase the turning effort or outward to decrease it.
  • Remember that the turning effort should only be measured at the centermost position; if you check it, you will notice that the turning effort drops off when the steering shaft is turned about one-half turn off center.
  • When the lash is adjusted, tighten the adjuster lock to the correct torque.