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1986 Chevrolet 1-Ton Steering & Hydroboost Brake Rebuilt - 4-Wheel & Off-Road Magazine

Chevrolet 1-Ton Steering & Hydroboost Brake Rebuild - Stop Steering At My Secrets Fred Williams Brand Manager, Petersen’s 4Wheel & Off Road 1986 Chevrolet 1 Ton Steering Rebuild Hydroboost Brakes Rebuilt 1986 Chevrolet Army Truck Photo 10766094

If You Can't Stop And You Can't steer your 4x4 then you're in for a dangerous ride, so it's a consensus that the steering and the brakes of your 4x4 are the two most important components. Since these systems can be extremely complex, we always recommend taking your steering and brake components to a professional if you are not 100-percent sure you know what you are doing. To simplify things we'll concentrate on a steering and hydroboost combination system. This is found in many heavy-duty trucks, especially those with diesel engines because they do not require vacuum to boost the brakes. We recently had the power-steering pump, box, and hydroboost system rebuilt on one of our project trucks. We also added a hydraulic ram for steering assist. If you've ever been inside any of these parts then you know how intricate they are, and if you haven't been then this will answer some of the mysteries within your hydroboost steering/stopping system.

1986 Chevrolet 1 Ton Steering Rebuild Hydroboost Brakes Rebuilt steering Kit Photo 10766100

This is one area we highly recommend using experts on. A mistake in any of these rebuilds could have deadly consequences because unlike a manual transmission or an axle, these parts are what keep your vehicle from becoming an out-of-control 3-ton chunk of steel hurtling down the trail or highway. We're not saying don't attempt to take your steering components apart, but we would recommend having a pro put them back together.

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PhotosView Slideshow The first order of business was taking the power-steering pump and box to Lee Manufacturing for a rebuild and boost. Lee Manufacturing is unknown in much of the off-road world, but the company has been building specialty steering components for many trophy trucks and desert racers for years. This is a P-style pump where the pump itself seals within its own reservoir as compared to the other commonly used TC-style pumps where there is an external or remote reservoir. The pump consists of the flow-control/piston assembly and the pump itself. From right to left is the flow control, the piston or poppet, and the piston spring. Consider this the door that the pressurized fluid opens and leaves the pump through. The piston floats within the chamber in case the backpressure overwhelms the piston. Backpressure occurs when the steering is turned to full lock and then pulled hard until the pump buzzes. This backpressure is bad for your pump because it recirculates and cooks the fluid. Inside the piston is a spring-loaded plunger that seals up against a small ball bearing. This is where the pressure for the pump is determined. As the pump pushes fluid against the ball and plunger, the spring is forcing the plunger against the fluid, causing pressure to build up, similar to the way a spring holding a door shut causes you to exert more pressure to get through the door. After the fluid has increased in pressure from the piston, its volume is controlled by the flow control. Lee Manufacturing bored out the flow control for additional volume since the new steering system will be using a hydraulic ram assist. The pressure line going to the hydroboost and then the steering box screws directly into the flow control on the back of the pump housing. The pump has (top to bottom) the thrust plate, pressure plate, ring and rotor with vanes, and then the driveshaft that is keyed into both the rotor and the beltdriven pulley. On the left is the original assembly and the larger parts on the right will increase the oil volume to help with the ram as well as boosting the volume at low engine rpm. This is helpful in rockcrawling since turning big tires requires extra fluid even though the engine is at low rpm. With the ring and rotor in the pump, notice how the vanes move in and out of the slots in the rotor as the rotor spins within the oval ring due to centrifugal force. As the space between two vanes increases, it forms a vacuum and pulls fluid in from the reservoir. Then as the space decreases it compresses the fluid. Then as the rotor turns it passes over an opening where the compressed fluid can escape and is routed into the piston chamber. The pump is reassembled with new seals and O-rings installed and a new end plate that makes room for the thicker ring, rotor, and pressure plate. Note that a reservoir from a hydroboost-equipped vehicle has two low-pressure return lines, one from the steering box and one from the hydroboost. PhotosView Slideshow 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.

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