Power Steering Conversion
By Jim Van de Ven
Last updated: 5/2/97
Drop me an e-mail: firstname.lastname@example.org
Pre-'72 Land Cruiser power steering conversion using a mid-70's International Scout II power steering box and pump.
-Before you go, buy a pickle fork, you will save yourself much frustration with old tie-rod ends.
-Don't go in the middle of a Minnesota winter like I did.
-Bring a high-lift jack and jackstands so you can get under the front of the Scout to work.
-Scout hoods release is in the middle of the dash, the hoods hinge on the front side (took me a while to figure this out)
-Take the pump, hoses, steering box, and tie-rod (not drag link). You might also want to take the belt for a reference at NAPA later. You don't need the steering column from the Scout.
-Find a Chevy with a straight six and power steering. The PS pump should look like the one from the Scout but with a bigger pulley. Take the PS pump bracketry from this engine (it mounts the pump above the alternator).
-Find a Chevy pickup with power steering and take the steering column from it. It has a rubber joint at one end and a universal on the other.
-Bring it home and clean off all the old grime. (engine degreaser works well)
Other necessary parts:
-A way to hold the steering column in place. I used a U-bolt spaced out from the fire wall brace. You could also use a piece of steel with a hole cut to fit snugly about the steering column and bolts to the fire wall.
-*A bearing or bushing to center the steering shaft in the column. ID 19mm, OD 35mm. I was only able to find a bearing what was ID 20mm, OD 35mm at the local bearing company (NAPA referred me to them). The 1mm backlash is hardly noticeable.
*note-I refer to the tube that does not turn as the steering column, and the inner rod as the steering shaft.
-U-joint 3/4" shaft to 3/4" shaft. (I found it at Fleet Farm)
-Locking ring for your Cruiser shaft to keep it from sliding back up. (Found near U-joints at Fleet Farm)
-1/2" steel pipe to reinforce the frame.
-fan belt (mine was 3" shorter than the original Scout)
-Power steering fluid
-Lift the front of the Cruiser and take off the left front wheel.
-Remove the left front fender and lower the front grill.
-Cut the old steering column right above the steering box (you can always cut more later).
-Disconnect the wires for the horn (bottom of the steering column near the pedals)
-Pull the steering wheel and column out through the cab.
-Remove the steering box, side drag link, and center arm. (You get to practice your rivet removal on the center arm) =8^)
-Remove the front shock to give yourself some room to grind.
-First objective is to get the gear box in place. You will need to grind off just about all of the inner rib on the shock tower. You will need to grind a space in the lower front of the shock tower for the bolt of the steering box to fit. You will also need to move your radiator over about 1/2 to 3/4" (the bolts holding the radiator can be accessed from the underside, just behind the front cross piece) Remember to tweak the fans shroud so your fan blade will not hit it.
Notice the amount of metal that needed to be removed from the shock mount.
-Once your box rests their without much interference, you can drill the rear hole. Do not drill the front two holes yet. Put one of your 7/16" bolts in to hold the box in place and allow it to pivot.
-Take your Cruiser steering shaft and cut it right behind where it flares out to a larger diameter. You will now have a rod that is 19mm which is basically 3/4" (1.9cm/2.54=.748")
-Cut the Cruiser column so that the shaft will stick out about 3" further than the column.
-Reinforce the column by either using a U-bolt that connects to the firewall support, or by some other method.
-Put your bearing inside the end of the column. It should be snug.
-Slide your steering shaft back into the column, being careful not to punch out your bearing. Also be sure that the wire for your horn also makes it back out through it's hole and grommet.
-Add a locking ring to the shaft with a washer behind it. This will keep the shaft from sliding upward into the cab. The washer will put the force on the column and not on the bearing when the shaft is pulled up.
-Slide one end of the U-joint onto the end of the steering shaft. Tighten down the cotter key. Put a board, or some other barrier in front of your engine (keep sparks out from where you don't want them), and *weld the U-joint to your steering shaft.
*Note-whenever welding on your truck, make sure you disconnect the negative ground from the battery, otherwise you will fry your battery.
-Now measure the distance from your steering box to the U-joint or your steering shaft. Cut the upper universal joint off of the Chevy shaft. Take the Chevy steering shaft and drill out the plastic crush pins. Shorten the length of this shaft so it will fit with one end on the box and have the other end, with the FF U-joint, matching up with the U-joint on your steering shaft. (to slide the shaft, you might need to persuade it with a hammer)
-Put the other piece of the U-joint on the Chevy shaft and match it up with the box so that when the steering wheel is straight, the steering arm is pointing directly ahead. Tighten the cotter key, remove the shaft, and then weld the U-joint to this shaft.
-Now rotate the steering box until their is least amount of angle in the rubber joint in the Chevy steering shaft. Mark the two front bolt holes and drill them. Remove the box and the Chevy steering shaft.
-Drill the holes. Where the frame is completely boxed, drill a larger diameter hole on one side so that it will allow your pipe to slide in until it hits the other side of the frame. Mark and cut your pipe so that it is flush with the outside of your frame. Weld the pipe in place and grind off the excess so it is again flush with the outside edge of the frame. This will keep the frame from crushing when you tighten the bolts.
-*Bolt back up the box and insert the Chevy steering shaft, readjust the length of the shaft if you need to. insert the inner X in the U-joint and put the chevy shaft between the box and U-joint. Bolt it all together and put the inner snap rings on the U-joint.
*One tip- After bolting in the box, it is difficult to insert the Chevy shaft. Loosen your locking ring on the Cruiser shaft and slide it a couple inches back into the cab, this will give you the clearance you need to get it in there.
-Redrill the holes for the crush pins and put in new bolts.
This is how the linkage fits with the fender in place.
To mount the PS pump on an F engine with double pulley, you can use the bracket from the straight six Chevy engine while still keeping your alternator in the same place.
-Remove the top adjustment piece from the alternator.
-Bolt a straight piece of steel onto the Chevy bracket, this will attach to where the alternator top bracket was.
-Adjust the angle between the piece of steel and bracket until the bracket can be held still and the alternator can sweep along the entire arch with a bolt in the bracket.
-Remove the Chevy bracket and weld this piece of steel to the bracket near the end. Discard the retaining bolt and grind off the excess of the piece of steel.
-Check the fit of the pump bracket elsewhere, I had to grind some off the back side.
-Bolt in the bracket and readjust the tension of your alternator belt. Put the Scout PS pump into the bracket.
-Check the length of the Scout belt (it should attach to the front of the two pulleys). Go to your local auto parts store and get a belt that will fit your truck. Mine was 3" shorter than the Scout.
-Put in the belt, and tighten it up. Connect the hoses that were still on the pump. Fill it with power steering fluid. Turn the wheel back and forth a few time to circulate the PS fluid. Add more fluid. Do this several times.
Left: Shows how pump mounts above alternator and takes the place of the top slide.
Right:Shows how the belt runs to the second pulley on F engine, right between fan belt and fan blades.
-Cut the Cruiser drag link near the left tie-rod end.
-Cut the Scout tie-rod at an angle near the bend in the rod. (The angle cut will allow for more welding length)
-Measure the length from the end of the pitman arm to the Cruiser tie-rod end. Mine was 37"
-Unscrew the Cruiser tie-rod end from the drag link. Slide the Cruiser drag link into the Scout tie-rod. (It is a tight fit, so some persuasion might be necessary. Once they are the correct length, weld the two together. Make sure this is a very good quality weld.
-Bolt the drag link back in and tighten down the clamps.
-Congratulations, your done. You will now have to go to a gym to keep the muscling in your arms :)
Other Off hand Suggestions
-You might want to find a shorter pitman arm off another vehicle. Using the Scout pitman arm, you only have about 2.5 turns lock to lock. This will be great for the trail, but a little too quick for the highway.
-When reinstalling your sheetmetal, you will find that the front clip has a parking light that will interfere with the steering box. I removed the bulb and bent the light housing up. I then had to drill into the lower part of the housing to be able to reinsert the bulb at the new angle. I would also recommend bending the sheetmetal out on the fender, then once it is bolted up, pound it back in around the box. This will keep some of the grime out of your engine compartment.
Some Information from my Research
Stock Cruiser Steering:
Before 1972, Cruisers used a low efficiency steering gear. This gear has an efficiency of about 60-80%.
Steering gear ratio=3.75*360 degrees/67 degrees=20:1
Steering wheel radius|
Turns lock to lock
Full angle sweep of pitman arm
Pitman arm length
Center arm input arm
Center arm output arm
Maximum force through drag link- Most Extreme case
Torque in steering wheel=(.75')(50 lbs.**)=37.5 ft*lbs
**25 lbs per hand
Torque out of gear box=(37.5 ft*lbs)(20/1 gear ratio)(80% efficiency)=600 ft*lbs
Force in side drag link=(600 ft*lbs)/(6.75"/12")=1067 lbs
Torque of center arm=(1067 lbs)(5.5"/12")=489 ft*lbs
Force in front drag link=(489 ft*lbs)/(6.5"/12")=903 lbs
Scout Steering box:
I ran a test with the Scout power steering box. I tested the box from 0 to 800 psi at an incriment of 200 psi. Here is some of my data and calculations.
Oil Pressure (PSI)|
input torque, no pressure
Torque output (ft*lbs)|
Force in drag link (lbs)
The torque output in this chart only represents the added torque of the power assist. To find the actual maximum torque output, the driver input also needs to be added. The Scout box also has a ratio of 20:1. The box is a Saginaw box that uses a very efficient worm and roller gear. I have heard that the gear is about 90% efficient. Stock it has a pitman arm length of 9.25" (I might try to swap mine with a shorter one later).
Torque in steering wheel=(.75')(50 lbs.**)=37.5 ft*lbs
**25 lbs per hand
Torque out of gear box=(37.5 ft*lbs)(20/1 gear ratio)(90% efficiency)=675 ft*lbs
Force in drag link of driver=(675 ft*lbs)/(9.25"/12")=876 lbs
Force in drag link of assist=(716.1 lbs)-(173.8 lbs)=542.3 lbs
Force in drag link total=(876 lbs)+(542.3 lbs)=1418 lbs
Bottom line, the Scout box puts out 515 lbs. more force into the drag link with a longer pitman arm than the Cruiser. It has a more efficient type of gear, gets rid of two extra tie-rod ends, and turns quicker than a stock Cruiser. Just be careful not to break things with the extra power.
This conversion is at the owners risk and I assume no part in any ill fate that might occur because of my directions. Use at your own risk.
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