C1 Steering Box Restoration - Restoring The C-1 Steering Gear

Straight Steer From A Vintage Worm-And-Roller Gear!

Moses Ludel Sep 9, 2009 0 Comment(s)
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Chevrolet engineering dominated the chassis and front suspension of the original Corvette while the steering and suspension designs came mostly from Chevrolet passenger cars. For the steering gear, Chevrolet drew on Saginaw Division's worm-and-roller unit, the standard fare for lighter G.M. cars of that period.

In 1940, Saginaw pioneered the revolutionary recirculating ball-and-nut steering gear. Heavyweight, upscale models like Cadillac, Buick, the Oldsmobile '98' and light trucks quickly benefited from the design. Chevrolet, Pontiac and lighter Oldsmobile models, however, continued to use Saginaw worm-and-roller gears. Less sophisticated, with fewer components, worm-and-roller gears were common to many postwar vehicles. Arguably, Chevrolet's first-generation Corvette might have benefited from a smoother, more precise recirculating ball-and-nut gear. A recirculating ball-and-nut gear offers closer tolerances, nimbler steering and a longer service life. Once again, the decision to use a worm-and-roller unit tied the Corvette to Chevrolet's 1953 passenger car models.

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Here is a prime incentive for rebuilding a C-1 steering gear. A previous owner stripped the steering wheel nut and threads on the steering shaft. Threads on the shaft are beyond repair, requiring replacement of the entire steering shaft and worm. Although the gear has only minor wear, a complete restoration is now practical.

By 1955, Chevrolet passenger cars dropped worm-and-roller steering gears, opting for Saginaw's recirculating ball-and-nut design. In defense of the C-1's worm-and-roller gear, the unit did offer greater stamina and better performance than the Gemmer gears used in '55-'57 Thunderbirds. More importantly, vintage racing Corvettes quickly proved their worth, and worm-and-roller steering carried through the C-1 era. Corvette did not acquire a recirculating ball-and-nut gear until 1963, being the last G.M. model to do so.

Design And Wear Points
A Corvette worm-and-roller steering gear has a ball-bearing supported roller gear. This is a plus, as the ball-bearings are rugged and generally outlast the life of the gear. The roller mounts at the inner end of a sector shaft, and the outer end of the shaft supports the pitman arm. A solid steering shaft has a worm gear at its base. The roller gear teeth engage the worm. As the steering wheel rotates the steering shaft and worm, the sector shaft pivots, rotating the pitman arm fore-and-aft.

The worm has tapered roller bearings at the top and bottom. This support is ample and provides many years of service. The upper end of the steering shaft rotates in a column bearing, which supports the steering wheel. An iron gear housing, needle roller bearing support for the sector shaft, and quality bearings on the roller make this gear reliable and rugged. By contrast, the Gemmer worm-and-roller gears use small needle bearings on the roller, and the sector shaft's support is two bronze bushings.

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The tale of damage began with the replacement of the turn signal switch. Use care when removing and installing the steering wheel. Cross threading the steering shaft threads is not only dangerous, it requires complete disassembly of the steering gear to remedy. This shaft has been ruined by careless workmanship.

Assuming a C-1's gear has proper lubrication, wear is predictable. Needle bearings, tapered roller bearings and ball-bearings will wear over time. Rarely is this wear so minimal as to allow for adjustment of the gear. However, adjustment can sometimes remediate minor looseness and provide additional service before the inevitable rebuild. If light adjustment can remove normal wear characteristics, and if the gear moves freely through its range of motion, an adjustment could be warranted.

More often, if you find that the sector or worm bearings require considerable adjustment, the gear definitely needs rebuilding. The roller teeth and worm can wear or pit, chip or corrode. Attempting to adjust out such play is dangerous. Overly tight, the worm-and-sector can bind or even lock up. Upon disassembly, the gear that requires appreciable adjustment will show sufficient wear for a rebuild.

Fortunately, unlike many other steering gears of the '53-'62 era, there are aftermarket rebuild parts available. Corvette America and Corvette Central offer an extraordinary rebuild kit for the C-1 steering gear. The kit is available for models with either '53-'57 or '58-'62 steering shaft lengths. A premium quality steering shaft and worm, a new roller with inner race and bearings, worm bearings, sector needle roller bearings, a sector shaft seal, cover gasket and upper column bearing with new horn wire round out the package.

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Getting the steering gear to this stage begins with disconnecting the pitman arm and draglink while in the chassis. If necessary, loosen the gear from the frame and rotate slightly to access the sector. Use a pitman arm puller to remove the arm. Follow the ST-12 manual's steps when removing and installing the steering gear assembly. Unless damaged, the mast should be left in place during the rebuild.

This rebuild kit provides all wear parts except the sector shaft and sector adjuster. The new roller kit must be used with the original sector. This is fine as long as there is no spline wear, thread wear or excessive wear at the sector's adjuster slot. The fit between the adjuster thrust washer, button head and the slot is precise and critical. Excessive thrust clearance is an issue. The adjuster clearance or correct fit within the slot must be restored.

Before Rebuilding, Separate Steering Issues
The '53-'62 Corvette steering system has many wear points that create steering looseness. Lack of lubrication, poor adjustment techniques and improper front-end alignment can also contribute to steering quirks. Before rebuilding the gear, which entails a good deal of effort to remove, pinpoint the wear and weaknesses in the Corvette's system.

Points of concern would be: 1) the kingpin bushings, causing shimmy and wheel wobble, 2) wander and sway from loose tie-rod ends, draglink cups or bellcrank/third arm bearings, and 3) loose wheel bearings creating wobble, shake and wander. Eliminate any of these wear issues before condemning the steering gear. If roughness or binding persists, disconnect the draglink from the pitman arm. Slowly rotate the steering wheel from left to right extremes, feeling for roughness or notchiness. Binding is common when the sector adjustment has been over-tightened as an ill-fated attempt to reduce overall steering play.

When steering won't return to center after turns, check for steering gear bind or insufficient caster angle at the front wheels. The caster angle should be 4-degrees positive, plus-or-minus 1/2-degree. Camber, caster, toe-in and toe-out on turns must each measure within specification. Total front-end alignment is critical and often overlooked on vintage Corvettes. Setting just the toe-in is simply not enough.

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Saginaw worm-and-roller steering is a rugged design. Compared to Gemmer and Ross manual gears of the period, the Corvette C-1 steering gear has much better sector shaft support and a superior roller bearing design.

There are numerous wear points on the front end of a C-1 model. Common checkpoints are much like a 1953 Chevrolet passenger car: the kingpins and bushings, tie-rod ends, steering knuckles and spindles, wheel bearings, control arm bushing wear, worn sway bar bushings, coil spring sag or a loose steering gear. Combined, these features make up the handling and safe steering of your vintage Corvette.

If your search narrows to the steering gear, approach this job with the 1953-62 Corvette Servicing Guide (ST-12) in hand. This factory workshop manual details the removal and installation of the steering gear, the overhaul steps and the proper methods for adjusting the gear. The book is available in reprint form from automotive literature and Corvette parts sources. Every vintage Corvette owner should have a copy. Consider the steering gear rebuilding steps. Decide whether tackling your gear is a home project or sublet to a Corvette restoration shop.

Set up properly, the C-1's Saginaw worm-and-roller steering gear is a rugged and reliable unit. If the original gear got your Corvette this far, a precisely rebuilt gear, with modern upgrade components, should easily last another half-century!

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