The following series of pics came from a Forum thread too, but I can't find
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.
Here are some other Hydro Assist Articles of interest: