Classic cars are never quite as good as we thought they were back when they were new. That 500-hp Chevelle you had in high school really only made 260, and it handled like dump truck. Add 40 to 50 years into the mix and it is bound to be significantly worse off for wear, especially the steering. Manual steering is not awful when properly set up, but when a manual gearbox gets some age on it, the slop comes in fierce. If your steering box has more than an eighth of a turn of play, then it might be time to rebuild it.
Rebuilding a manual steering gearbox is not difficult and is much cheaper than buying a new one. Plus, if you have a valuable classic, keeping the original versus installing a replacement maintains the value of the car. This was the situation for my 1966 Corvette, as I was keeping it stock. Instead of converting to power or rack and pinion, I opted to rebuild the original Saginaw manual gearbox with a kit from Borgeson (p/n 921039). The kit comes with everything you need to rebuild a worn gearbox including bushings, gaskets, bolts, and the most important parts: the worm and sector gears.
This is a recirculating ball gearbox, which is essentially a giant double-grooved ball bearing assembly. The worm gear — the part of the gearbox that is connected to the input shaft — is a machined block that has the gear teeth on one side and two machined grooves inside the block. Metal ball bearings ride inside the block, providing the bearing surface for the grooved input shaft. As you turn the steering wheel, the bearings spiral through the worm gear block, moving the block up or down the input shaft. This movement is translated to the sector gear, which is attached to the pitman arm. As the ball bearings roll on the shaft, worm block, and each other, each component slowly wears down. This is where the slop comes from.
Eventually, you have to turn the wheel to take up the extra space that is left behind from the wear. This can become significant and that is dangerous situation. Yes, you can compensate for the play, but this also leads to lane drifting as the steering system will wander left and right without the tension inside the gearbox. The solution is a complete rebuild with a new sector and worm gear assembly.
To do this rebuild, you need a few specialty tools, mainly a small shop press, seal drivers, and an inch-pound torque wrench. If you want to replace every bearing race, then you need a Kent-Moore J-5288 and J-5755 bearing cup puller/installer tool, but this is not necessary in most cases, and you can reuse the original races. In fact, the instructions state to only remove the races if necessary. We used a gallon of Carb Dip for the small parts and a five-gallon bucket with diesel fuel to clean the case. All of the old grease needs to come out, considering it has a lot of grit and metal shavings in it that will reduce the life of the replacement components.
Aside from the cleaning, the entire rebuild process takes a couple of hours. I let my parts soak overnight to get them clean, but you could put in some more elbow grease and get the job done in a couple more hours. With the rebuild, the 1966 Corvette steering box is nice and tight like it should be, set to factory specs, and ready to be reinstalled into the car.