The heart of the system is the Danfoss Steering Unit, seen here with the steering shaft attached.

Shows the input end of the steering unit, as well as the 4 threaded holes to which a) the steering input shaft bolts; and b) the steering unit is mounted to the vehicle.

This is the Performance Off-Road Systems custom steering shaft. The splined section is specifically manufactured in 36 spline .750" ,which is the common automotive steering shaft spline size, to fit standard automotive parts, as opposed to most other shafts are a common agriculture size that sends you searching for agricultural parts to match.

From the center hole of the filter it flows up through this column that is in the middle of the reservoir, and exits through 2 small ports in the column (red arrows indicate location), that are about 1/2-1" below the top of the column.

This arrangement is designed to reduce aeration of the fluid as it returns to the reservoir. It is a form of baffling. Finally, the fluid exits through the large circular port in the bottom of the reservoir (yellow arrow)...

The CFR has a steel 1/4 turn cap attached by a small chain.

This leads me to my first, hopefully constructive, criticism. The cap supplied with the CFR is a fully sealing kind. As discussed in Part 2, and indeed as Sean himself recommends, the system should be run vented. However, a vented cap is not supplied, nor available, from Performance Off-Road Systems or from any other source that I could find (and I tried all kinds of gas, oil, and radiator caps - buying several to try).This leaves you with only 3 choices:

1. run the system sealed (I wish I had actually just tried this first - as it would turn out that I would have a bit of a nightmare time with plumbing the system),
2. install the supplied CFR as an auxiliary reservoir only, below the level of some other suitably vented reservoir; normally a stock attached-to- pump reservoir. (This solution is unsatisfactory for several reasons - chiefly the difficulty in mounting this CFR below the level of a stock pump reservoir and also the fact that many of us may be using Saginaw TC or aftermarket pumps that don't have any integrated reservoir)
3. modify the supplied cap to vent. This is the option I chose, and it was a HUGE pain in the butt.

...held on the backside with a pipe coupling I cut in half to produce a sort of NPT "nut" to hold all the little bits back together with the nipple fitting.

This led to another little SNAFU. As you can imagine, through this process, the exact orientation of the little locking tabs of the cap changed somewhat. While getting them re-aligned so the cap would go on and off easily enough but still stay tight the steel galled the aluminum of the lip of the tank and left me with a small pile of aluminum shavings in the bottom of the tank - as you can imagine - not the best of things for a hydraulic reservoir!

All in all - nothing major, possibly caused by my own ineptitude, but like I said, a royal pain that could easily be avoided with a proper vented cap offering.

This beast is custom designed and built to spec specifically for off-road hydro steering systems on hardcore rock smacking machines. You won't find any other available quite like it, and it is FAR superior to any other offered.

It has a 2.5" bore , 8" stroke , 1.5" diameter IHCP( Induction hardened, Chrome plated) shaft and .25" wall thickness on the body of the cylinder. The length is 21.5" + the length of the clevice ends.

Built to take a serious beating, able to handle the unique stresses of rock crawling, and easily able to handle the pressure of the most hi-po pumps and generate tremendous amounts of steering power...this beauty may not be shiny but it definitely gets the job done!

Two of the rod ends are 3/4" shank and 5/8" ball bore and are used to connect the rod end of your mini tie rods to the clevis end of the cylinder (pic at left). the other 2 rod ends are 3/4" shank and 3/4" bore for attaching the other end of your mini tie-rod to the knuckles steering arm.

As can be seen at left, 6 small machine washers are included for use with each clevis, to center the rod end between the jaws of the clevis.

I found, however, that the supplied socket head cap screws left the threads between the jaws of the clevis, so the washers and rod end would be bearing against the threads instead of the full 3/4" shank diameter.

I used an old shaft from an F250 that had this neat flexible coupling that, of course, fit perfectly onto the steering shaft from Performance Off-Road Systems.

The other end of the column (really just a solid 3/4" steel shaft) runs through a bearing for support under the "dash" and then has the quick-disconnect coupling for my steering wheel welded to it.

No matter how robust the cylinder, you don't want it left vulnerable, hanging out front to get damaged.

I built a large truss from 1.75" tubing angled forward and up in front of the axle to serve as both a skid plate / guard for the cylinder as well as a place to mount the cylinder.

You can see from this pic that the cylinder is extremely well protected.

Clearance from the diff cover is an issue. Not only must the cylinder shaft obviously not hit the cover, but it would also be a large PITA to have to remove the cylinder every time you wanted to remove the cover.

We managed to get my cylinder positioned so that it clears the cover, the cover can come off without moving the cylinder, and yet the cylinder is not too far offset to one side of the axle.

Mini tie rods have to be constructed to connect the ends of the cylinders shafts to the steering arms on the knuckles.

A side shot showing the positioning.

The cylinder does not have to be mounted dead center in the middle of the axle (which is a good thing, because if it did, either the diff would be in the way, or you would have to have it stuck way too far out in front).

However, you should not mount it such that it is more than 30% off center. this is because, the more off center it is, the greater the difference in length between the 2 mini tie rods. If the shorter of the tie rods gets too short, it will have to move in too much of an arc as it's knuckle steers from full left to full right. As it moves through this arc, if there is too much of an angle created between the knuckle and the cylinder shaft, undesirable side loads can be imposed on the cylinder shaft that can wear or damage seals or the shaft itself.

having said that, the Performance Off-Road Systems cylinder is the biggest and strongest available, specifically designed to be able to handle some degree of side-loading.

Here you can see what I mean about the angle of the tie rod.

In these initial installation pics, you will notice that I am using my OTT steering arms.

However, a problem readily became apparent with the use of these arms with my new setup / geometry.

Because the OTT arms are designed to be able to accommodate virtually all combinations of rims and backspacing, the distance from the center of the kingpin to the tie rod holes is quite short, in the order of 4.5" I believe.

This means that, in order for the cylinder and tie rods to all lie in a nice straight line, the cylinder itself would have to be mounted virtually directly on top of the axle tube.

And the problem with that approach is that you would need a lot of "lift" in order to create the space necessary and not have the cylinder smacking the crank snout or radiator or chasis.

However, this created tie rod angles I am not happy with and also resulted in me being unable to use the cylinders full 8" stroke.

As I write this I am currently working on a new steering arm setup that will have the kingpin-to-tie-rod-hole distance closer to 6.5 or 7". This will allow full use of the entire cylinder stroke and allow me to keep the mini tie rod in a straight line with the cylinder shaft when the shaft is fully extended and at it's most vulnerable.

Stay tuned for an update later on....

When setting up the cylinder, you also need to account for any cylinder stroke not used because of your geometry. In other words, you MUST have the cylinder run out of stroke before, or right as, the steering stops are reached.

This is because of the enormous force possible from the system. If the steering stops hit before the cylinder is out of stroke, and the pump is producing healthy flow and pressure, it is quite conceivable that continuing to turn the steering wheel after the knuckles reach their stops would simply shear the knuckles right off the housing.

If you look closely at these early testing pics, you can see that the geometry (short steering arms to be precise) only allowed for 3/4 of the cylinder's stroke to be used (you can tell by the wear markings on the cylinder shaft). This is probably what allowed the rod end to get bent as the cylinder continued to push to that side after the steering had run out of travel, and the weakest link, in this case the rod end, deformed under the load.

Here's the modified P-style Saginaw pump used in my initial system. Note the 5/8" suction line supplying fluid to the reservoir from the remote auxiliary cooler/filter/reservoir assembly.

After struggling with some strange plumbing problems, the worst of which was the vented reservoir from Performance Off-Road Systems puking hydraulic fluid out the top of a 2' vent hose, that we couldn't fully troubleshoot before I lost my mind in frustration, I ended up replacing the pump and suction line, as well as deleting my Hydroboost brakes all in one go.

These pumps are high volume pumps with standard flow of 2.5 GPM. With the interchangeable flow valves the flow can be set anywhere in the range 1.5 GPM to 3.7 GPM. These units have the same pulley offset and mounting pattern as the GM Saginaw style pumps.

They run at 1350-1450 psi, and I chose the highest flow of 3.7 gpm to feed my steering unit.

Once you have everything installed and plumbed, it's time to fill and bleed. The procedure I discovered works well is:

1. Fill reservoir to just over tip of column
2. Raise front tires off ground to remove resistance
3. Turn steering wheel lock-to-lock while constantly checking the reservoir for air bubbles and level drop. Top us as necessary - be careful not to over-fill. When no more air appears to bubble out and the level remains constant, go to step 4
4. Check fluid level in reservoir, disconnect coil wire, and crank engine over to operate pump and flow fluid through entire circuit. Crank in short bursts. When no more air appears to bubble out and the level remains constant, go to step 5
5. Re-connect coil wire.
6. Check fluid level in reservoir and start engine. Operate at low rpm's at first, do not turn steering wheel. After a few seconds shut down engine and check reservoir. It will likely look like the pic at left, frothy and full of air bubbles. Allow bubbles to dissipate (can take upwards of an hour) and repeat this step until frothing does not occur.
7. Check fluid level in reservoir and start engine. Operate steering lock-to-lock while constantly checking the reservoir for air bubbles and level drop. Top us as necessary - be careful not to over-fill. When no more air appears to bubble out and the level remains constant, go to step 8
8. Top up reservoir, install reservoir cap, lower front tires to ground.

1. Cylinder ports
2. Cylinder
3. Tie rod
4. Cooler
5. Pump
6. Steering Unit
7. Hoses to Hydroboost brake booster (deleted in final system config)
8. Hydroboost booster (deleted in final system config)
9. Cooler/Filter/Reservoir

This was the first obstacle on the first trail on my first ever day of testing. At this time I didn't have the tie-rod / steering arm geometry right, the presumed dysfunctional hydroboost booster was still plumbed in the system, and the old worn out pump was running the show. As a result the reservoir was puking fluid out the vent hose and into a catch can bungee tied to the hood.

Even with those limitations, the steering was superb.

In this pic, with the old steering gearbox setup, and with me being in welded front low-low with drive slugs in the hubs, steering in a situation like this would have been impossible. I'm just about high-centered, and the front tires are over but still up against the rock while the rear tires are just meeting the back side of the rock. With forward progress stopped, steering the old fashioned way would be impossible. Not only that, but I would have been forced to dismount and press the winch into service.

Not so with my new hydro steering. Even in a situation like this, with no forward progress, essentialy stuck, with welded fromt diff, I could easily steer back and forth with only 2 fingers and the engine just idling.

In the end I was able to just wiggle the steering back and forth from this position, grab some traction, and pull my self over the boulder.

Actually, that was an unexpected by very cool advantage to the mod - I never thought of hydro steering as a traction aid, but throught my expereince and testing so far i have found many times that the ease of steering allowed me to wiggle around and find traction in situations that before would have left me hung up and looking for a yank or winch. VERY COOL!