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C1 Steering Box Restoration - Restoring The C-1 Steering Gear
Straight Steer From A Vintage Worm-And-Roller Gear!
Sep 9, 2009
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C1 Steering Box Restoration - Restoring The C-1 Steering Gear
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.
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.
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.
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.
These illustrations (courtesy of the 1953-62 Corvette Service Guide, ST-12) show the layout and operation of the gear.
To compensate for leaks, the original lubricant was gradually replaced by chassis grease. A rebuild will restore tolerances and includes a modern sector seal in place of the original packing type.
Once cleaned, bearings can be pressed from the gear housing.
The upper bearing cup is a challenge. A special (rare) G.M. puller removes this tapered bearing cup and the adjuster race. Another technique is to weld a pair of one-inch string beads at opposite faces of the old cup. Carefully confine these beads and heat to the race cup, and do not damage the housing! As the beads cool, the cup collapses slightly and slides loose. Here, a new cup seats snugly with a cup driver tool and hydraulic press.
New needle roller bearing presses into the housing bore. Needle cages must be pressed from the reinforced, square end of the bearing shell. Use a press lube like Sunnen's B-200L Lubricant to protect the housing. Each bearing should rest at its original position. Wipe away lube before packing grease into the bearings.
The new worm is a sturdy replacement design. Available from Corvette Central, Corvette America and other suppliers, the worm shaft and roller kit is a boon for C-1 owners. Many restoration projects depend upon NOS parts. These contemporary parts enable a quality rebuild to factory specifications.
New worm and steering shaft replace the damaged original shaft. The worm-and-roller gears must be a matched set. Replica shaft and roller show quality materials and machining. Cost to repair the damaged original shaft would exceed the price of the entire rebuild kit. C-1 owners should take advantage of current parts availability.
Balance of the kit contains all needed parts for thoroughly rebuilding a C-1 steering gear. Note quality of components. Each wear point is considered. Bearings, column bearing, the cover gasket, sector seal and a new roller assembly address the wear points. A molded draglink seal and pitman arm nut are additional pieces not included in the kit.
Hard parts get glass bead blasted. This cleans, de-burrs and restores surfaces. The original sector shaft is in excellent condition and gets a new roller and bearing assembly. Since the shaft itself is usually in good condition, the kit does not require a shaft. Needle roller bearing in the side cover can be carefully peened inward with a punch. Protect castings when removing or installing bearings.
Roller consists of outer tooth and inner race assembly. Ball bearings run between these parts. The original through bolt ("shaft") and nut will be reused. The bolt shown is strictly for holding the assembly together for shipping. This precisely machined set of parts will restore performance to like-new level.
The original, factory shaft-bolt and hex nut secure the roller assembly in the sector. Bolt and nut torque is 55 ft. lbs. Apply Loctite 271 (red) to clean threads. The sector flanges pinch the inner bearing races together, preventing the races from rotating on the shaft in service. Pack the ball bearings with chassis grease.
Once the shaft-bolt is secure, the exposed threads require peening. This is the factory method for preventing the nut from coming loose. Peening crushes the threads toward the nut. Done properly, the peened thread sections lock the nut in place, preventing it from loosening in service. Do not overlook this safety measure.
The rebuild kit includes a new upper column bearing. This provides a new horn wire as well. Before installing the new worm and steering shaft, carefully press the upper bearing into the column tube. Be certain to align the wire properly, using the original, factory routing as a guide.
A correctly lubed column bearing and renewed brass horn ring are an important part of gear restoration. The bearing is not readily accessible once the steering wheel is in place. Greased and fresh, the bearing supports the upper steering shaft. For the bearing to function properly, install the steering wheel's spring and other hardware in the right order.
Pack the tapered worm bearings with grease. Coat the worm surface with grease as well. By now, you have installed new bearing races in the worm adjuster cup and the gear housing. The threaded adjuster cup will set the load on these bearings. Coat the adjuster's threads with a thread sealant to prevent gear lube seepage.
Temporarily mount the steering wheel on the steering shaft. An alternative, shown, is to fabricate a lever arm with nut. The arm's spring scale hole is drilled to match the radius of the steering wheel. Before testing the worm bearing adjustment, grease the sector bearings and temporarily install the sector shaft with side cover. Keep the sector adjustment loose to prevent any drag. Worm bearings require a 3/8- to 5/8-pound pull at the steering wheel rim. Pull at right angles to the spokes.
Once the worm bearings are adjusted properly, secure the large lock nut without rotating the adjuster. (Avoid the hammer and punch method on this nut. A suitable chain wrench will tighten the nut securely without leaving a mark.) Again, turn the gear gently to its left/right extremes, pulling with the spring scale. New bearings can be set closer to the 3/8-pound pull.
For final assembly, coat the adjuster screw, cover bolt threads and side cover gasket with sealant or Gasgacinch. The adjuster thrust washer controls clearance between the screw's button head and the sector slot. This gap should be 0.002" or less, measured with a feeler gauge (shown from ST-12 manual).
If there is too much adjuster-to-sector play, Chevrolet's fix is the rare NOS assorted-thickness washer kit, part #605142. New adjuster screws are available in the aftermarket or as NOS part #7802482. Back off the adjuster screw and tighten side cover bolts with lock washers, evenly and securely.
Working on a variety of gears, the fabricated tool is handy. The stock Corvette steering wheel measures approximately 18" diameter. The lever hole is equal to the rim of the wheel. Pull the spring scale perpendicular to the arm or a steering wheel spoke. Over-center, a "high point" increases drag and should read a total pull of 7/8- to 1-7/8 pounds. Once correct, hold the adjuster screw and tighten the lash nut to 15-20 ft. lbs. Again, check the full left-to-right range pull.
Fully adjusted, the entire gear gets a primer sealer coat. Mask off the sector splines and threads. Also, mask the upper steering shaft threads, splines and the brass horn ring. This is an epoxy primer, and it will act as a quality base and sealer for the catalyzed commercial enamel color coat.
Color coat is a semi-gloss black as per the owner's preference. Factory match would be a flatter black mast, a gloss upper turn signal cup and silver gear housing. The cover coat should be paint with excellent adhesion and resistance to oils, heat and grease. Once cured, you can protect the mast for installation with a wrap of masking paper.
Ball stud masked, the glass-beaded and clean pitman arm gets its coat of primer-sealer and color. Avoid painting the splines, as this can cause a false torque setting during installation. The pitman must fit tightly on the sector splines. You will install the pitman arm after the gear is in the chassis.
Here, the masked column tube protects the gear during assembly. Getting the gear in and out of the car is not easy. This job requires two people and care. Suspend the upper column temporarily with tie straps while aligning and attaching the gear to the frame. The firewall plate, loosened during installation, should hang loosely on the column.
Cast frame spacer and factory hardware now have the gear positioned on the frame. Torque the nuts to 35 ft. lbs. with new, properly graded lock washers. Use Loctite 242 on bolt threads for added safety. Allow hardware and parts to settle. After loading the gear, re-torque these nuts.
Pitman arm has been installed with the gear in the chassis. The nut torque should be 120-125 ft.-lbs. Use Loctite 242 and a fresh, graded lockwasher to secure the pitman arm. Replace any worn draglink parts. Install and adjust the draglink plug to factory specifications. Secure with a fresh cotter pin. New dust seal holds grease in the joint.
This plate must hang on the column tube during installation! After the gear is fully in place, install the plate and caulk the seam. Use the original dust-hole cover seal if intact. If not, replace the seal. Here, air conditioning caulk assures that engine bay fumes and heat will not enter the driver's compartment. Caulk the inside floorboard, too.
Prior to operating the gear, fill the housing with lube. For a moderate climate, use a 90W-120 or similar EP gear lubricant. The factory fill was "SG" (steering gear) lubricant, similar to 90W gear lube. Multi-viscosity lube provides better protection when the engine heats up the steering gear. After driving the Corvette briefly, check and top off the lube to the bottom of the fill hole threads. While chassis grease is often added to offset a leak problem, the modern sector seal should retain gear lube for many years.
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