Homebrew hydraulic-assist steering for a Toyota truck
By Carl and Vonski @ RockLogic4x4- Member's of Wild Yoat's Toyota 4x4 Association
This article will deal with installing hydraulic-assist steering on a 1988 Toyota truck, which has been converted to use a solid axle from a 1985 truck. The modifications will be similar for any solid-axle truck using a Toyota IFS style steering box.
The decision to try this setup was an easy one, since Von frequently had a difficult time steering his 35 x 15.50 SX’s at 5psi. Sometimes the wheel would violently jerk out of his hands and pitch the truck a direction other than where we wanted it to go. We already had a 6” stroke Howe steering ram sitting around the shop waiting for a home, which was a great match for the “high steer” system already in place on the rig. (If you have standard “low steer” crossover, you’ll need a ram with a longer stroke)
You’ll notice in some of the pictures that the front end of the truck is nekkid-it isn’t necessary to tear the whole front end down, but we were doing some other mods at the same time.
If you are considering putting your steering box at risk by modifying it yourself, then I’ll assume you have the tools necessary to complete this job. At minimum, you’ll need basic hand tools, a pitman arm puller, a drill press, and an appropriate drill and tap for the holes. (We used ¼” NPT) Also, be prepared to spend a lot of time cleaning the metal shavings out of the nether regions of the box. We found a small magnetic probe very helpful, as well as generous amounts of brake cleaner.
If you don’t feel comfortable doing this work yourself, there are reasonably priced kits available that include the ram and mounts, the lines, and the box modifications for around $200.
Remove the pitman arm.
Remove the steering box from the frame. We took a little bit of extra time to trim the inner fender, which gave us far easier access to the box.
Turn the input shaft so the box is approximately centered.
Remove the 4 bolts from the top cap-you can leave the adjuster nut in the center alone.
Tap on the end of the sector shaft with a rubber mallet or dead-blow hammer to remove it along with the top cap. Be prepared for a bunch of oil to drain out.
Turn the input shaft all the way counterclockwise; you’ll see the piston inside moving toward the input shaft.
Remove the 4 bolts from the input shaft housing.
If your box has one, remove the 10mm allen head screw from above the piston, and remove the centering valve. (red arrow) In this picture, the box on the left is from a 1993 truck and you’ll notice we already tapped it, and the one on the right is the original 1988. We’re using the 1993 box, because the input shaft is longer than the 1988 version.
We moved the steering box forward, so the extra length meant we didn’t need to extend the steering shaft as far.
Pull on the input shaft housing to remove it along with the piston.
Locate where you need to drill the holes, mark them carefully with a center punch. The hole on top is more critical (and dangerous) because you’re drilling into an existing passageway. If you drill too far, the box becomes garbage. The other hole is easier, and there are two spots you can drill into. if you’re planning on moving your box forward, don’t drill into the “TOYODA” stamp, because the hydraulic line plumbed to that hole will interfere with the body mount. Otherwise, feel free to drill a new “A” hole. J
Drill and tap!
Clean everything VERY well-you don’t want metal shavings floating around your power steering system.
Reassemble in reverse order. Be careful when installing the piston, there is a sharp lip that can catch one of the Teflon rings.
We mounted the ram from the top of the differential to the tie rod, and had custom hoses made up by Evco House of Hose. Connect the hose from the top of the box to the fitting farthest away from the shaft of the ram. This port provides pressure when turning left, which will cause the ram to extend. Obviously, the other hose goes on the other fitting. (Duh)
Now that everything’s back together, it’s time to bleed the system. “Bleed” is a pretty accurate way to describe the process, since it seems inevitable at some point you’ll have red fluid spewing out of the system. Begin by topping off the reservoir. Start the truck and slowly cycle the steering back and forth. The fluid will become foamy. Shut the truck off and wait for it to settle. Top off the fluid again if needed. Start the truck again and while running, crack open the bleeder valve on the top of the steering box until fluid flows out. Some boxes have this bleeder (looks just like a brake bleeder), and some do not. If it doesn’t, loosen the adjuster nut on the top, as it will serve the same purpose. Repeat the above steps until air is purged.
Now go out and experience the joy of turning at will. CAUTION: You will be able to turn the wheel slightly faster than the ram can react. It takes a little getting used to, but it is worth the sacrifice.