These are the replacement parts for a Gemmer worm-and-roller steering gear. A new roller a
Do not rely upon the steering wheel position to determine the center point of the steering gear. If necessary, disconnect the steering linkage at the pitman arm and gently rotate the steering wheel lock-to-lock. Carefully count the turns. Divide the total by two, and slowly rotate the steering wheel halfway back from one steering extreme or the other. This should be the approximate midpoint or "high point" of the gear.
On manual steering gears, the high point indicates the closest mesh of the gear teeth or lever pins. This is the point described in adjusting specifications as the over-center mesh adjustment. Mesh adjustment is read in this zone of steering.
Before checking or adjusting mesh, check the worm or cam bearing adjustment. Ball, barrel, or tapered roller bearings support the upper and lower ends of a worm or cam. If the bearing load or endplay is too tight or loose, make this adjustment. Too tight would only occur if the gear has damage or someone over tightened the bearings. After adjustment, make certain the bearings feel smooth and do not bind. When any more than a slight worm bearing adjustment is necessary, the gear likely needs rebuilding.
The old worm and roller stands out next to the new parts. The notch in the old worm was ca
Once the worm bearings are set properly, you can test the over-center mesh. Rock the pitman or sector shaft up and down to check for wear at the shaft bearings or bushings. If the sector bushings or bearings are within tolerance (matching the shop manual's specifications for shaft side play), gear tooth or lever pin mesh can be tested accurately. Follow the steps in the manual to measure the over-center mesh. Again, any more than a slight adjustment indicates excess parts wear.
You will discover that manual gears have pitman backlash as you move the steering away from the center high point. Do not mistake this play of the pitman arm for excess backlash. Notice that as you steer back through center, the backlash at the pitman arm goes away. In actual driving, the backlash off-center is not felt. If caster angle at the front wheels is set correctly, there will be no wander from this backlash. The close mesh over-center provides good road feel with the wheels in the straight-ahead steering mode.
A final consideration is alignment of the front wheels with the center point of the steering gear. Everyone wants even steering wheel spokes when the road is straight. However, this is not as important as making sure the high point of the steering gear indexes with the front wheels in the straight-ahead position. Start by aligning the front wheels with a toe-set bar or on a commercial wheel alignment rack.
New shaft bushings or bearings should be installed with proper tools. Bushings often come
Find the center point of the steering gear. This may require disconnecting the steering linkage at the pitman arm. If the steering linkage is adjustable, align the drag link or center link so that the steering gear is in its center position when the front wheels point straight ahead. Once the gear is on-center with the front wheels pointed straightforward, you can position the steering wheel correctly.
On many vintage trucks, the steering wheel can be positioned anywhere in a 360-degree range. Some models have a fixed (woodruff keyed) steering wheel location. When the steering gear is on its high point, the steering wheel is straight. There is usually a provision in the steering linkage (an adjustable drag link or center link) for centering the gear's high point while the front wheels point straight ahead.
Any more than a slight mesh adjustment indicates excessive parts wear. Always check for roughness and binding after adjusting the mesh. If gear teeth have chipped or lever pins have worn flat (common on high mileage steering gears), adjustment is futile and risky. The gear may lock up or bind in service. Make plans to rebuild the unit or upgrade to a more modern steering system.
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