DIY: Saginaw Box Rebuild.

Tech article written by Dave Ashman



Some more pics of a Saginaw rebuild, but not a full rebuild:


I have an 88 jeep Cherokee XJ; I have the stock 3in bore Saginaw power steering box. The J20 Jeep truck power steering boxes are a nice junkyard upgrade because they have a 3.5in Bore(more power). The J20 boxes should be fairly easily to modify and fit to smaller.


I rebuilt my stock box it was in ok shape, but leaky. If your box is badly worn and loose you may want to find a low mile J20 box, rebuild,and drill it for Ram Assist. The stock PS pump will work with the J20 box but you will need some adaptor fittings at the box.


I bought the Saginaw rebuild kit from $48

Here is a picture of the rebuild kit from WTO.



Box Disassembly instructions:

1. First remove the pitman arm
2. Remove the three steering box bolts holding it to the frame.
3. Place an oil sheet on the floor, and then remove the high pressure and low pressure hydraulic lines going into the power steering box. About a qt of fluid will come out, keep the lines tied up and clean. You could cap them with some tape to keep them clean.
4. Remove the sector shaft from the input of the power steering box. Be careful the box is heavy when it comes loose. The box should be free to take out.
5. Move the box to a clean bench work area. Get a bucket handy to catch the oil trapped inside the box. Remove the c-clip on the bottom of the pitman arm shaft. Remove the top 4 bolts at the other end of the shaft. Make sure the pitman arm is centered (turning straight position). This shaft will pull out. Fluid will pore our when the shaft is removed.

6. Now remove the LARGE c-clip at the end of the box. At the top of your box there is a pinhole (probably full of dirt) push through the pin hole to help get the clip out. With pliers you can turn the splined input shaft of the box. Turn it counter clock wise and the. This will move the big piston and push the cap out the end of the box. If you see the big piston spinning inside the box and not screwing out you could put the pitman arm shaft back in to help hold it from spinning.

7. With the pitman arm shaft out and the cap off, keep turning the input shaft till the piston comes out of the end of the box. You will probably hear the bearings fall into the big piston. They will, so donít loose any.
8. Now remove the c-clip at the steering wheel shaft side.
9. With a hammer you should be able to tap the ring counter clockwise (yellow in my pics). The ring has three indentations on it you can tap on. Screw it out. This may require some PB blaster if your box is rusted. You could also apply some heat. All the seals in there will be replaced any ways. Then the spiral shaped shaft and smaller piston (The spool / orbital motor) will pull out.

(Optional steps 10 and 11 see the Ram Assist Tech Article)

10. Now you can drill the holes for the ram. The top hole will drill all the way through. I used a 1/8in bit for pilot holes to keep it centered. The bottom hole only drills half way into the box till it hits a hydraulic line hidden inside the casting. Both holes will be drilled to 7/16in (look at the pics for locations)
11. Tap the new holes with a 1/4in NPT tap. The top hole is easy, but the bottom hole will only go till the tap bottoms out. I then cut about 3/16in off the tip of the tap, then continued with the bottom hole till it bottomed out again. The tap was like $6 at Home depot.

12. Clean the inside and outside of the box with a solvent (paint thinner) to get all the grit and oil out. I used a wire brush then did a final rinse with water, and used an air sprayer to get all the metal shavings and liquid out. Paint it and stuff.
Then put the 3/8in to -6aN fittings on the box using pipe tape for the Hydraulic Ram Assist.
13. Put new seals on the pistons. kinda tedious. (see pics)
14. Re assemble.

Pics of the internal parts and seal locations:

The internal parts:


The Pitman arm shaft has a new bearing on it then there are a series of two oil seals separated by a metal washer. There is another washer after the final seal before putting the c-clip back on.


The steering box end cap on the steering shaft side has a new needle bearing, new oil seal, and a new rubber washer seal. Ill take pictures of this on my next box rebuild. (future update)


The large 3in piston, with the spiral shaft in it:

The Bearings roll through the little bent tube you can see in the pic above. When you remove the spiral shaft the balls fall into the 3in piston. I used thick bearing grease to hold the bearings in place inside the large piston. I then screwed the spiral shaft in from the other side of the box on re-assembly. The large piston has a new rubber seal under the new purple seal.


The small piston:

This smaller piston is called the spool / orbital motor. This is the power assist portion of the box. The piece picture is three pieces: The Torsion Bar, inner collar, and the outer piston. The splined steering shaft is a torsion bar that twists an inner collar hidden inside the piston. The inner collar has flutes cut in it to actuate the flow of fluid and begin the power assist.

Push the torsion bar down and out, then replace the one O-ring on the inner collar. Replace the three O-rings and the three purple rings on the outer piston. These three pieces can only be assembled in one way, you will know if you do it wrong.

When I was done I had this pile of old seals:


Tech Article Written by Dave Ashman, (ashmanjeepxj)†††††††††††††††††††††††††††††††††††††† ††††††††††††† ††††††††††††Last updated 02/25/04