(The following tech information was taken from the Pirates of the Rubicon Bulletin Board and from an email exchange between Todd Thomas and Reuben Gosewisch)
Topic: Homemade hydraulic assist steering for under $250!! Explained!!
BMSN123 posted 04-07-2001 07:07 AM
I did this once about 8 weeks ago and very few people caught on. I guess that it was not flashy enough.
I think that I claim the right to have done hydraulic assist steering this way for the first time. Roughly a year ago I needed help with the steering on my scout (about 6500lbs, D60 Front, 38.5's, detroit in front)because it refused to turn sitting still even with the pump boosted. I broke out my IH manual (2 inch thick one) and studied how the steering box worked. All this was about 1 month before the AGR rock ram system came out so I was on totally new ground. Anyways I had a idea and this is how it developed and it did work the first time.
The power steering gear (all) has a piston with a rack gear on the side and that is what gives the boost. AGR taps in at the valve for their hydraulic assist. I tapped in on both sides of the cylinder because it was easier (and I did not understand the valve portion yet). I tapped my box in the two alluminum plates on it. One is on the end of the box and the other is where the adjustment for the steering lash is. Beleive me it works! These two caps are on the two sides of the cylinder and that is where I brought my lines down to the cylinder. The top cap you have to take the adjusting lock nut off and then the four bolts that hold it on and screw it off of the adjusting stud. Then drill and tap a hole (for whatever fitting size you deside to use, I used 9/16-18 and used a compression o-ring type fitting but I showed another guy and he used pipe thread fittings) beside the adjusting stud (look for a small recess on the bottom side) and try to hit that spot. I suggest that a machine shop drill and tap your holes on both plates so that they do not leak. The cap end you need a punch to knock the retaining ring out. There is a small hole somewher around the body of the gear on that end. If you find that hole and drive a punch in it it will drive the retaining ring out enough that you can grab it with pliars and pull it out. Unlike the adjusting cap this end cap is thin so I would have someone weld a 1/4" piece of alluminim to the end cap and then drill and tap the hole through it just like the other cap.
I used a 2"-8" stroke ag cylinder from farmers supply as my steering cylinder. A dana 60 axle will use a 8 inch stroke cylinder. Smaller axles will use less stroke and the cylinder has to stroke out before exceeding the original travel of the tie rod. To measure the stoke you need turn the wheels to lock one way and measure from some point on the tie rod to the side of the spring. Turn the other way and subtract the difference and that is the stroke cylinder that you need. When you get your clinder set like you want it and it is stroking out both ways I suggest that you remove your steering stops because now your cylinder is your stops.
Local hydraulic shop should be able to make your lines and provide the fittings, or you can get everything from a Northern Hydraulics cataloge. They are on line
Run lines from the steering gear down to your cylinder. Start the vehicle and DO NOT PULL HARD ON THE WHEEL, YOU VERY WELL COULD HAVE THE LINES CROSSED and with the tires off of the ground the wheels should drift from center to one side on there own. If you try to turn the wheel and there is resistance stop and switch your lines.
The bigger the cylinder the slower it turns but the stronger it is. I would not go over a 2 in bore cylinder.
Especially Jeeps put a skid plate over the end of the gear box. You do not want to hit that fitting anc chance causing it to leak. Keep the lines out of the way.
I suggest a big cooler and additional resevoir capacity. I even run a inline hydraulic filter.
A two inch bore cylinder will double the turning force.
This should work on any saginaw steering gear that I have ever seen.
Tell me what size end cap you have or send me yours and I can modify and put the fittings in for $100 exchange.
2"-8" cylinder $70
Lines and fittings $75
Machine work on caps $50
Metal for mounts $20
No labor because you do it yourself
Let me tell you, AGR is making a killing!!
I know of 4 vehicles that I have helped with this setup and 2 more in the process of being put together. I need a digital camera!
Member MTTR (is that the same DRM?)
I was doing a search through the POR archives on hydraulic steering and came across information that you had done this on your scout. I am interested in doing this to my trail rig since I run a steering gear off of a scout. If you have any documentation and picures of the modification please let me know. Any information would be appriciated.
Reuben Gosewisch TLCA#9965
Basically you remove, drill and tap a hole for a hydraulic fitting into the two alluminum caps on the gear box. One is beside the adjustment screw with the 4 bolts holding on
and the other is the end cap with the snap ring holding it in. I could make a set of those plates like on mine for $100 exchange for yours, $25 core charge;).
I know that it sounds nuts but hydraulic pressure does not have to come from the same spot AGR brings it out and those caps can be done without totally disassembling the gear and risk of contamination. Run your hoses from there to your cylinder and you have home grown hydraulic assist. If you can do all the fabrication you can have the basic setup for $150. (75 cylinder + 75 hoses and fittings) I suggest a cooler and a larger resevoir.
Any questions feel free to ask.
Thanks for the information on the hydraulic assist. The pictures also help out. A couple of questions. How much assist does it give? Does it drive on the street well? What size of hydraulic cylinder did you use? And did you just tap the covers with NPT thread, or some other type of fitting, and how did they seal? How do you like the modification?
Thanks again for all the information
2.5x the turning force
Fine on the street but slow compared to what you are used to
I used 2"bore - 8" stroke
9/16-18 thread with O-ring fittings
Love it in the woods and better than a steering stabilizer
I forgot one last question, Does it matter with hose goes where?
where should each one be plumbed into the cylinder?
Yes it does but just try it easy with the pitman arm disconnected and make sure it is right. It depends on how you mount the cylinder.