Chevrolet 1-Ton Steering & Hydroboost Brake Rebuild - Stop Steering At My Secrets

Following the course of pressurized fluid, we delve into the hydroboost before proceeding to the guts of the steering box. For the teardown and rebuild of the hydroboost brake booster, we headed to Vanco Power Brake Supply. Vanco has been building powerful hydroboost systems since the early '90s, when they realized that the hydraulic booster system resulted in two to three times more pressure to the brakes than a normal vacuum booster-a great upgrade for trucks with massive tires to slow down. The Vanco team quickly had our hydroboost disassembled into what looks like a jumbled mess of springs, rods, and pistons. The parts to the far left are what's inside a normal master cylinder, while the parts to the right make up the hydroboost system.

This system takes the hydraulic pressure from the power-steering pump and uses it to boost the pressure to the master cylinder. From left to right is the power piston that is depressed by the pushrod attached to the brake pedal, which opens a spool valve allowing fluid from the power-steering pump and the accumulator to go behind the piston and multiply the force going into the rod going into the master cylinder.

If you happen to be steering at the same time as braking or the engine shuts down then the hydroboost has a nitrogen-charged accumulator that acts as a back-up pressure source. The early accumulators (right) used a massive spring to make pressure, but eventually it was discovered that a nitrogen-charged chamber with a floating piston similar to that used in a shock would be sufficient. The charge is good for one or two full power-brake applications without pump pressure, and after that there is still manual braking.

Vanco has a few proprietary upgrades to help the hydroboost flow a larger volume of steering fluid when combined with the Lee ram assist that we swore to secrecy not to reveal. Instead we'll show you this trick remote hydroboost. Designed for hot rods or small 4x4s or buggies that don't have room on the firewall for a normal hydroboost, this can be mounted anywhere and uses a slave cylinder that depresses the pushrod from a master cylinder at the brake pedal. In addition, Vanco has brackets to mount its hydroboost systems on the firewalls of everything from Scouts to fullsize trucks to Jeeps even if they didn't come so equipped.

After the pressurized power-steering fluid flows through the hydroboost, it then heads down to the power-steering box. We assumed the power-steering gearbox would be the simplest part of the system, but it turned out to be the most fascinatingly complex component of all three. The job of the folks at Lee Manufacturing was to tear down the box, modify it for a hydraulic ram assist, and reassemble it while explaining how it all works. They did a great job of all, but we're still boggled with all that's going on inside the steering box.

Did you know that a steering box has a torsion-bar spring like those found under an IFS chevy only much smaller? The torsion bar determines the feel of the steering-a skinny flexible torsion bar will have a soft feel, whereas a thicker bar will have a heavier feel. The torsion bar is a coupler between the steering wheel and the sector shaft that turns the wheels, and as you turn the steering wheel the torsion bar twists.

The torsion bar is also the central control inside a spool valve. The spool valve (seen here with the new blue seals) is what controls the pressurized fluid and determines if it should bypass the box and return to the reservoir or flow through the box and help it push a piston back and forth. As the torsion bar twists, it opens the valve to one or the other side of the piston. The spool valve is also attached to a ball screw that screws into the piston and causes it to move up or down within the piston chamber in the steering box.

If you ever had a steering box apart then you've likely come across a ton of little ball bearings. These act as the thread for the ball screw. As the ball screw screws into the piston, the piston needs to move up and down within the steering box. But rather than try and cut threads into the piston, the balls are used so that the piston can be rebuilt and adjusted. What you may not know is that those little balls are different sizes and they must be measured and installed in a certain order.

As the piston moves back and forth inside the box, a sector shaft that is keyed into it rotates. The sector shaft has a pitman arm attached to it outside the box that forces the drag link back and forth and thus steers the wheels.

There are both variable-ratio steering boxes and single-ratio steering boxes. The boxes use different pistons and sector shafts. The piston on the left is variable ratio such that as you turn farther to one direction the steering quickens. In high-speed driving slight steering-wheel movement doesn't have a quick reaction in the wheels off center, but when slow steering such as in a parking lot you can quickly point the tires as you get farther from center. The straight-cut piston (right) keeps the same ratio throughout the entire turning cycle and can be twitchy, slow, or just right depending on what ratio is used and what speed the vehicle is traveling.

Our box has Lee's signature ram-assist fittings TIG-welded in place and drilled for the fluid. The placement of the fittings is determined so that Lee signature steering fluid flows to a different fitting depending on which direction the steering box is turning. The assembly of the box is a black art where lots of little pieces need to be installed in a specific order and various bearings need to be set for proper preload both within the valve and at the top of the sector shaft. Proprietor Tom Lee has been building steering boxes for many years and has built many of his own test fixtures to pressure-test boxes for leaks and pressure specs as well as pumps for optimum performance before anything is shipped.

Even after we had all our freshly rebuilt parts back from Lee and Vanco, we still had to install them and mount our new hydro-assist ram. Master fabricator Karl Knoll from Off Road Unlimited quickly had some tabs welded to our front Dana 60 and we were ready to slowly bleed any air bubble out of the system by steering the wheel back and forth for a few minutes until the truck was steering the truck was one-finger easy.