Steering Gearbox Adjustment

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Revision as of 02:18, 22 February 2015

No amount of free-play adjustment will fix a worn out steering gearbox. But for normal wear, the proper adjustment can make a significant improvement in steering feel. Well worth doing on any 1200 over 10 years old or with more than 80k miles.

top of gearbox showing square filler plug, and hex adjusting nut

Determining Need

More than 25 mm play in the steering wheel? Car wandering slightly side-to-side on the highway?

Try this test: with car stopped, use one finger to rotate the steering wheel a bit one direction then another. You should have less than 1 inch of play. If you have more, it's probably the linkage or the gearbox (or often both). The tires won't be a factor in this test.

If the play -- when wiggling the steering wheel back and forth with your fingertips -- is more than 20-25mm (3/4 to 1 inch), tighten the steering box. After 30 years of use the gears wear a bit and can be adjusted.

Wider tires can make the vehicle 'wander' when moving down the road. Wander is the tendency to not move straight ahead but to have little movements left and right seemingly at random. Adjusting the toe-in should minimize it.

It's normal for 1200 steering to feel 'vague' in a straight line. Even the reviewers back in 1971 said so if I recall correctly. Factory specification is 20-25mm at the steering wheel rim (about 1 inch).

You can check the steering linkage as follows:

1. lie on the ground near the driver's side door, looking at the underside of the car
2. reach up and wiggle the steering wheel back and forth (with the door open)
3. watch to see if any of the rods move independent of each other. If they do, the rod ends need replacement.
4. the steering knuckle, and thus tires, should move with the tie-rods
5. the idler arm should NOT move up and down

This can be easier if a mate handles the wheel, leaving you free to inspect the underside, but it can be done without an assistant.

To double check any of the rod ends and idler arm, jack up the wheels and securely block the car, then wiggle the rod end ends forcefully by hand. There should be no play; they are supposed to rotate, but not move end-to-end or side-to-side.

Finally, if in doubt, disconnect the rod-ends, they should move with a firm but smooth drag as you rotate them. If they flop around, they are worn out.

Process

You don't need to jack the car up. Don't turn the adjusting nut a fixed amount, just take the slack out of the adjuster. If you tighten it too much, the steering could get heavy and accelerate wear of the box.

The proven method (regardless of what the manual says) is this:

Of course you'll want to confirm that the steering linkage is tight first, because that's usually where the play is. The tie-rod (side rod) ends, ends of the drag link (cross rod), and particularly the idler arm should be inspected first. If those are in good condition, adjust the steering gearbox.

1. Turn wheels straight ahead. It is important to adjust the lash when the gearbox is centered. Otherwise it will be too tight in one direction.
2. Loosen locknut (14mm), turn counter-clockwise as usual
3. Tighten adjusting screw with a flat-bladed screwdriver, just finger tight. Do not apply any real torque
4. Tighten locknut