You love driving your prewar car down the highway. Cruising the crowded city streets is a massive boost to your ego. Parallel parking or maneuvering in close quarters however, is a trip to hell. You could have a problem with your steering box.
The steering box of the prewar drag link steering system is a simple affair. Generally, described as the cam and lever type, they require very little attention with the exception of proper lubrication and keeping the bolts tight.
The basic box works like this. The steering wheel turns a shaft with a steering worm gear. A cam attached to a steering shaft lever rides the worm gear and transmits the movement to the trunnion shaft, or steering cross shaft. The trunnion shaft rotates and transmits the movement to the steering arm and from there on to the front wheels through a drag link. Toss in a few bearings, perhaps an adjustment bolt or shim, and put it all in a cast box to house the works and provides a solid mounting point to the frame of the vehicle. Fortunately, this simplicity means very little can go wrong with the box. When it does, it means either harder steering or sloppy steering.
One of the most common problems encountered is poor adjustment. It is a requirement that there be a small amount of play or lost motion in the steering. Without it, the steering components will bind under load. This small amount of play with gradually increase over time. Often the process is so gradual that the driver does not notice it until it has become significant. When the play does become noticeable, or objectionable enough to be noticed, readjustment is necessary.
Before making any adjustment, raise the front wheels of the car off the ground and support the front axle so the wheels turn free. It is difficult to assess the amount of adjustment necessary when fighting the drag of the wheels on the ground. It is also advisable to adjust the tie rods and drag link to ensure there is as little lost motion in the steering linkages as possible.
Generally, if the steering wheel moves up and down, there is too much cam thrust clearance. To adjust this, the thrust nut must be turned. This nut is usually located at the top of the box where the steering column tube enters the box. The nut will be locked in place and this lock will have to be loosened in order to make adjustments.
The thrust nut should be tightened until the gear binds. This binding will be detected as the steering wheel is turned. Once the binding point is determined, the nut should be backed off slightly to free the bearing and allow the wheel to turn freely. Once this is accomplished , securely tighten the locking mechanism to ensure the thrust not does not back off.
If the steering wheel can be turned an excessive amount without a corresponding turning of the wheels the trunnion shaft requires adjustment. There are generally two ways this adjustment is made. Depending on the manufacturer there can be an adjustment bolt, or shims. If the box is equipped with an adjustment bolt or screw, it will be located on the side of the box. The adjustment will press against the end of the trunnion shaft and move the shaft.
With the front wheels off the ground, and placed in the straight ahead position, loosen the locking nut and turn the adjustment bolt or screw. As the adjustment is turned the play in the box will diminish. There must be some play remaining however, as rapid wear of the gear will occur from excessive pressure once driving resumes.
In the case of boxes that employ shims, the procedure requires removal of the side plate on the box. Generally, this can be done with the box installed in the car. Be sure to place a small pan below the box prior to removing the side cover to catch steering box lubricant. Between the side plate and the box are a series of thin metal shims. Shims are removed to eliminate excessive end play. The amount of shim removed will depend on the amount of excessive play needs to be removed. Appropriate shimming is often determined through trial. Once the proper shimming has been determined, the plate and shims are installed, bolts tightened and proper lubricant replaced.
Once end play is removed, turn the wheels from full stop right to full stop left to ensure there is no binding in the box.
Regardless of the type of steering box employed in your prewar car, proper lubrication is crucial to proper operation. Generally a fluid type of gear lubricant is used. Properly adjusted and lubricated it will give you years of trouble free service.
Tags: cross shaft, prewar car, proper lubrication, trip to hell, vehicle, wheel, wheels, worm gear
