Where to Tap a Saginaw Power Steering Box for Hydro Assist
By BillaVista

(actually - all photots are from PBB contributor's - I simply compiled and posted them here)

The following are a couple of threads on the PBB Forums regarding Hydro Assist box tapping:



The following series of pics came from a Forum thread too, but I can't find it.

If you know, or if you know who'se pics they are, please PM me at Pirate4x4.com so I can give proper credit where it is due.


The top port (blue arrow) is the port that will have high pressure when the steering wheel is turned left.

The lower port is the one that will have high pressure when the steering wheel is turned right.

These descriptions assume a standard Saginaw orientation of steering wheel and box.

Commonly the holes are drilled and tapped to 1/4" NPT.

That would mean drilling a 7/16" hole, then using a 1/4' NPT tap (18 Threads per inch)

The Left port (blue arrow) is drilled centered on the box casting seam (not sure this is true for all boxes)

The right port (green arrow) is drilled inline with the stock port indicated by the red arrow.

A schematic showing the fluid flow.

Pic and info courtesy of TORC.

The above boxes all sit on the inside of the frame rail like on a Jeep. If you have a box that sits outside the frame rail (like a Scout or Ford) and tapped it in those locations, the lines would be coming out right into the frame. My PS box mounts to the outside of the frame so I had to tap it in different locations. One of the ports (the one on the bottom rib of the box) I just moved to the other side of the box. I could have moved the other one to the other side as well, but there wasn't very much meat on that side of the box and I didn't feel comfortable tapping it there. Instead, I put the other port on the top of the box by the existing two ports.

'nuther view

Here are some other Hydro Assist Articles of interest:

BC 4x4.com article

West Texas Offroad Saginaw box modification

River Cuty rockcrawlers article

I Lean's Excellent Toyota Hydro Assist Article


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