As early as 1997, we knew we wanted to install a hydraulic steering system on Highlander, but it was low on our priority list.  After breaking the saginaw steering box while being pulled out of a DEEP hole at the last run of '98, we decided that we had to install the hydraulic steering before starting the 1999 mudding season.

Here's how our hydraulic steering installation went.

Find the steering valve.

We purchased our steering valve from a local used tractor parts company, basically a junkyard for farm equipment.  Our particular valve came from the steering on a Massey combine, and cost us about $45.00.  Since the valve isn't what caused the tractor to be scrapped in the first place, and don't usually go bad, the junkyards have a ton of them laying around that they are glad to get rid of at a reasonable price.  You can also get the valves from Boyce Equipment, but they are considerably more expensive, and basically the same valve.

When you pick out a valve, make sure you know how you will run the hydraulic lines to it.  A few of the valves that I saw had less or more than 4 ports.  While there must be a way to run the hydraulic lines for these valves, they may not work with a stock power steering pump, so be careful.  I selected a valve with 4 ports, and couldn't be turned by hand but didn't seem seized.  According to the junk yard, this type of valve shouldn't be able to be turned by hand unless connected to hydraulic power.

After purchasing the valve, I went to a local hydraulics company to have the valve tested to make sure that it worked.  We simply connected their hydraulic power unit to the input and output ports.  Then, once power was applied, I was able to turn the valve and verify that hydraulic fluid was sent to the left and right side ports of the valve.

Once we knew that the valve worked, I had to modify the input shaft of the valve to accept a standard universal joint yoke with a keyed bore.  As the valve came, it had a splined input shaft, and the original u-joint yoke was no longer attached.  Since finding the correct yoke was not likely, I decided to pick up a yoke from a farm supply store, and modify the input shaft.  It was turned down to .750" diameter, and machined for a keyway to allow it to be connected to our existing steering setup.  As it worked out, the yoke that I had purchased used the same u-joint as what was already in our truck (donated from a 1970's Scout).

With the valve prepared, we now had to mount the valve.  Jason fabricated a bracket that mounted the valve to the body mount framework that we had built.

The steering's intermediate shaft was then lengthened to fit the new steering location.

Next we mounted the steering cylinder to the front axle.  In order to fit the cylinder, the unused shock absorber mount was cut off of the axle tube.  The cylinder that we used was a 2" bore, 6.5" stroke with tie rod yokes at both ends purchased from a discount hydraulics shop.  The stroke length was measured by lifting the front of the truck, and measuring how far the tie rod moved from extreme left to extreme right wheel travel.  We chose a cylinder stroke that was slightly shorter than the distance we measured.  This allows the cylinder to stop itself, and puts less stress on the front axle when in tight left or right turns.

We tack welded the mount to the axle tube.  We will make the final welds later, after we have made sure everything looks right.

We were a bit more cautious with the other mount.  We had to make sure that when the steering was at either end of travel, that the cylinder and mounts didn't interfere with anything.  We were also worried that we would bend the tie bar since we were still going to use the stock tie bar.  We decided to use the same basic shape on this end as we did on the other end, since we didn't have any interference.  We did, however, widen the base to spread the stress across a larger part of the tie rod to help prevent bending it. 

Before tack welding the mount in place, we cleaned off all of the paint and rust from the area of the tie rod that we would be welding to.  Once the surface was ground down to bare metal, we tack welded the mount in place.  After welding, we jacked up the front axle so that we could test the steering travel and hydraulic line clearance.  The tests showed no interferance, and the steering travel appeared to be equally balanced between left and right.  Since we had no problems, and were happy with the steering travel, we completed the weld job.

Here you can see more clearly the 'top hat' shape of the mount.  This shape should spread the stress that the mount will see sufficiently to keep the tie rod from bending.  We're not certain if it is really necessary, but I would rather go through the work to do it now instead of later.  We will also be welding a piece of angle iron to the tie rod to further reinforce it.

Since the stock power steering pump runs off of the motor, we had concerns that if the truck ever died, we wouldn't be able to steer.  To prevent this, we decided to install an auxilliary power unit in the system.  The power unit is simply a hydraulic pump powered by a high power electric motor similar to a starter motor, and was purchased from Grainger Industrial Supply.  As it happened, since our battery is mounted in the bed of the truck, the existing battery tray made a perfect mount for the aux. power unit.

Now that all of our components were installed, we needed to determine what kind of fittings and hoses would be required to hook up all of our goodies.  We also had to design the hydraulic circuit to run the system.  Here is the resulting circuit:

This was the circuit and the components necessary to complete our system.  You should check through these and make sure that they will work for your application.  To give you fair warning, the hoses and fittings alone can add up to around $500.00 depending upon where you get them.  If you plan ahead, you can get them for sometimes much less, but you have to be willing to shop around, and have the time to find them.  In our case, we had little time, but got a good deal from A-1 Hydraulic Sales & Service in St. Paul, MN, who were willing to spend one on one time with me in selecting components, and even stayed well after closing helping make sure I got everything that I needed.

Installation of the components was fairly straight forward, though it took more than 4 hours.  A disproportionate amount of time was spent wrestling with the power steering pump, and trying to get the compression fittings to fit over the stock steel tubing.  Much of the trouble centered around the distortion caused by the bends put in the tubing at the factory.  Also, there wasn't much room left for the fittings once the stock ones were cut off.  Routing the rest of the system went well, and I was very cautious to fill the cylinder, and as many of the lines as possible to make working the air out later easier.

With installation complete, I moved on to testing the system.  Since I was performing the installation while the truck was still on the trailer, I disconnected the cylinder from the tie rod before starting the truck.  This made sure that if something went wrong, and the cylinder extended or retracted completely, there would be no danger of the truck coming off of the trailer.  As things worked out, however, the test proved that the system worked flawlessly (except for a little air left in the lines).  I reconnected the cylinder to the tie rod, and made sure that it could turn the tires with the full weight of the truck on them.  There were no problems, and haven't been any yet!