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Tapping Ford Box for Hydro Assist


Atomic Test Lab Rat
May 21, 2020
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It seems most of the older threads from various other forums all have pictures that are dead. I need to drill and tap the Box on my 88 F250 for my PSC ram. If I remember correctly there are a few locations these can be tapped. Who has the pictures/ tips for that?
How about a pic of the box you have. I have 2 different boxes I can get pics for you.
I'm driving right now but there's a good write-up on the ranger station that I used. Box is the same as a full size

Edit: I'm hauling the wheeler I can snap a pic when I stop
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Little square flat spot at the front of the box
Big flat square towards the back of the box
Sorry for the shitty gas station pictures
Hyde's photos are on-point. :beer: You're looking to tap into the pressure that feeds each side of the piston.

This is not a Ford box pictured below, but the views inside + 'splainin' might help someone:


A planned upgrade, the priority of which the DW elevated, was hydro assist – the ultimate steering stabilizer!
Here are a few photos of my steering box apart so you can see where the magic gnomes live.

Box coming apart. Reference marks are always handy, and buy a silver Sharpie if you don’t have one.

The two small holes are the passages for hydraulic pressure to reach either side of the piston in the steering box.

The two areas you drill and tap are each fed by one of these passages. The “+” is fed by the lower of these 2 holes.

The “+” in this picture is at the end of the passageway fed by the upper hole in the previous photo.

The horizontal chamber below the "+" is where the piston on the end of the rack rides.

In the block on the left, there is a valve that directs hydraulic pressure to one of the two passages depending on which way you are turning the input shaft.

The input shaft is also the worm gear that moves the rack. Hydraulic pressure on the piston assists the worm gear to move the rack.

Here are the two ports that feed passages that reach the two sides of the piston.

The teeth on the rack (in linear motion) drive the teeth on the Pitman shaft (in rotary motion), and the splines on the Pitman shaft turn the Pitman arm.

I got lucky: my Pitman arm was not sloppy, my seals were in good shape, and I didn’t fook up anything while I modified and reassembled the box.

You guys and gals that did your hydro tapping without disassembly have more faith than I do in the ability to remove all the debris.
I deburred and cleaned inside after drilling and tapping, and went full clean-room paranoid (within reason) at reassembly.

The 2 capped AN nipples are where the hoses take off to feed my PSC ram.
The brass pipe plug is where I wanted to run one of the hoses (but I decided to not modify the coolant bottle, so I went "traditional").


Hope that^ helps. I know clear pics were a bitch to find when I was first researching tapping a box.
Little square flat spot at the front of the box Big flat square towards the back Sorry for the shitty gas station pictures

I will confess a couple years back I attempted a rebuild and drilled and tapped the stock box from this truck. Its buried underneath a bunch of other stuff so it wasnt till I saw your pictures that i remembered where i drilled them. When I tossed it back on it was leaking bad from the steering input. I was still driving the truck at the time so I put on a remanufactured box and havent touched the other one since.

So now I have to decide if I want to try to rebuild the other box again or just pull apart this "new" box and drill it instead, which is the way I'm leaning.

What size fittings are you running on the box?
1/4npt fittings on mine

Edit: 1/4npt threads in the box, 1/4 male to 3/8npt female fittings and 3/8npt lines. There are better fittings but this was part of my $100 hydro project.

I would still do 1/4npt threads in the box and convert from there
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Had mine tapped by PSC way back in 06, here's where they did it

This is the better place to do it, but if I recall correctly, it can be difficult to get your feeds directly off the servo doing it at home. When you tap from the ends of the piston, all the fluid for both the box and your ram has to travel through the small passages in the box which can be a major flow restriction since you are essentially feeding your ram in series with the box. By tapping directly off the servo as shown in this picture, you are feeding the ram in parallel, and the fluid for the ram is not having to travel through the small internal passages in the box.
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