When Chevrolet introduced the new Corvette in 1963 it was hailed as a technological breakthrough, and when 1968 rolled around the C3 was about as close as one could get to a spaceship on wheels. Ironically, both these vehicles that were so groundbreaking in their time had one bit of technology that dated back to before WWII: the recirculating ball steering gear.
Introduced by Cadillac in 1940, recirculating ball steering uses a worm gear inside a threaded block. Imagine holding a screw with a nut on it—turn the screw one way or the other and the nut moves up or down on the threads. In a steering box the nut has teeth that mesh with the sector shaft that has a gear on one end and the Pitman arm on the other. As the steering wheel is turned the nut moves up and down the worm, that turns the sector shaft and the Pitman arm moves to steer the wheels via an assortment of linkages (it’s all a lot less complicated than it sounds). Now, add a bunch of ball bearings between the threads of the screw and nut to reduce friction and you’ve got the basics of recirculating ball steering. The design reduced effort when compared to earlier types of steering gear and with the huge amount of surface the ball bearings provided, wear was reduced dramatically as well.
While recirculating ball steering is a decade’s old design it was a good one and as a result it was used in Corvettes until 1982. And while they were near bulletproof, just about everything wears out in time, including these rugged steering boxes. Generally, wear manifests itself with sloppy steering that can’t be adjusted, hard steering if slack in the steering is adjusted and lubricant that leaks out the sector shaft due to worn bushings, sector shaft wear, a bad seal or all of that.
On the subject of lubricant, our 1963 Corvette service manual specifies that after removing the forward and outboard top cover screws “steering gear lubricant” (read chassis grease) be injected through the forward hole until it comes out the outboard hole. A long held belief is the Corvette’s steering box was so close to the exhaust manifolds that the heat generated would cause gear oil used in most GM steering boxes to leak out, consequently grease was used to prevent leaks. The downside was the grease eventually turned into a big wad of crud that did little or nothing to lubricate the moving parts and they began to wear.
Dealing with a worn-out Corvette steering box can be a done a number of ways thanks to Borgeson’s array of products. They offer internal power steering box update kits, new replacement manual boxes, and for those who want to retain the original steering box rebuild kits are available. Two rebuild kits are offered: one for 1963-’67 Corvettes with a 3/4-inch/36-spline input shaft (PN 921-039) and one for 1968-’82 Corvettes with a 3/4-inch/30-spline input shaft (PN 921-038).
Once the box is removed from the car disassembly is simple enough, the only difficult tasks are removing bearing races from the housing and the worm bearing adjuster (but we’ve got an old trick for that).
With our ’63 steering gear completely disassembled we bead-blasted the parts that would be reused, cleaned them thoroughly and then reassembled the box in reverse order with new internal parts from Borgeson. Filled with lubricant and adjusted according to the instructions, our steering box was as good as new and ready for another 54 years of service.
1. Our original steering box was loose and leaked lube, a rebuild kit from Borgeson made it good as new (in this case, new was 1963).
2. Borgeson’s rebuild kit includes everything necessary to freshen a tired steering box. The worm shaft, ball nut and recirculating balls.
3. With the bolts removed from the top cover a light rap on the end of the sector shaft with a brass hammer popped the top loose.
4. After the sector shaft was removed, a screwdriver was used to remove the seal from the bottom of the housing.
5. The area of the sector shaft that ran in the lower bushing showed signs of wear and corrosion.
6. A punch was used to remove the locknut on the worm bearing adjuster. The adjuster was then removed, allowing the worm shaft assembly to come out of the housing.
7. This is the worm and nut assembly. There are 56 ball bearings in those tubes and nut. Thankfully, the replacement from Borgeson comes completely assembled.
8. There are two sector shaft bushings in the housing. We used a length of tubing to drive the old ones out.
9. This is the bearing race from the end of the housing. We carefully ran a weld bead around the surface where the bearing ran, when the weld cooled and shrunk the race fell out.
10. A new race and ball bearing was installed in the worm bearing adjuster nut.
11. Included in the kit was a new seal for the adjusting nut. A seal/bearing driver was used to make sure it was installed correctly.
12. The seal/bearing driver (with a larger disc installed) was used to install the sector shaft bushings.
13. With the bushings in place, the sector shaft seal was pressed into the housing.
14. The worm nut and sector shaft gear have tapered faces. Moving the sector up loosens the fit between the two and increases lash, lowering it tightens the fit and reduces lash.
15. On top of the sector shaft is an adjusting screw that threads into the top cover. Turning the screw moves the shaft up or down.
16. Before the worm assembly was put into the case, a new lower bearing was installed on the shaft.
17. With the worm assembly in the case, the top bearing was positioned on the shaft.
18. The worm nut is installed and tightened until a torque wrench on the input shaft reads 5-8 in-lb.
19. Once the worm shaft preload is set, the lock nut is installed and tightened (being careful not to move the nut and change the adjustment).
20. With the worm assembly centered in its travel, the sector shaft is given a light coating of lubricant and installed. At this point Borgeson recommends filling the gear with 11-ounces of EP-2 grease (we didn’t for the sake of our photos, but went back and did it later).
21. The new adjusting screw was slipped into the slot on the top of the sector shaft; the top was then installed.
22. With the top bolted in place, the adjusting screw is tightened until it takes 4-10 in-lb more to turn the input shaft than was required during the initial worm shaft adjustment.
Photography by the Author