Three different power steering boxes are found on these Toyotas. An early-style 4WD box was used on 1986 to 1988 pickups and 1986 to 1989 4Runners. Later-style boxes were used on 1989 to 1995 pickups and 1990 to 1995 4Runners. Externally the early and late boxes vary in that the input section of the box is about an inch shorter on the early version. Internally they differ as well. There are also two later boxes with the year split about 1991 to 1992. Externally these seem very similar, but inside the power piston nut and sector shaft gearing is different. Also, the later boxes have a quicker internal gearing ratio, taking fewer turns of the steering wheel to fully exercise the range of the box. All year boxes mount the same way, and the hose tap locations are the same.
These steering boxes work well for adding hydro assist and can easily be tapped to provide the pressurized fluid for the hydraulic ram. Essentially we are using the pressurized fluid exerted on one side or the other on the piston, and routing it to one end or the other of the hydraulic-assist steering ram. One line will be pressurized when turning left and the other when turning right.
Here is what it takes to tear down, tap, and reassemble a Toyota IFS steering box. This particular steering box was from a 1994 4Runner. Steering boxes typically leak a good bit of fluid during disassembly. The Toyota service manual provides a far more detailed description of the rebuild than what we can show here. Should you happen to fully unscrew the power piston during the process, you will spill out the ball bearings inside. The Toyota manual provides instructions for their reassembly, and we have used them with success in the past.
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