Hydro Assist

7/29/2019 Hydro Assist

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This article will deal with installing hydraulic-assist steering on a 1988Toyota truck, which has been converted to use a solid axle from a1985 truck. The modifications will be similar for any solid-axle truckusing a Toyota IFS style steering box.

The decision to try this setup was an easy one, since Von frequentlyhad a difficult time steering his 35 x 15.50 SXs at 5psi. Sometimes thewheel would violently jerk out of his hands and pitch the truck adirection other than where we wanted it to go. We already had a 6stroke Howe steering ram sitting around the shop waiting for a home,which was a great match for the high steer system already in placeon the rig. (If you have standard low steer crossover, youll need aram with a longer stroke)

Youll notice in some of the pictures that the front end of the truck isnekkid-it isnt 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 ityourself, then Ill assume you have the tools necessary to completethis job. At minimum, youll need basic hand tools, a pitman arm puller,a drill press, and an appropriate drill and tap for the holes. (We used NPT) Also, be prepared to spend a lot of time cleaning the metalshavings out of the nether regions of the box. We found a smallmagnetic probe very helpful, as well as generous amounts of brakecleaner.

If you dont feel comfortable doing this work yourself, there are

reasonably priced kits available that include the ram and mounts, thelines, and the box modifications for around $200.

Remove the pitman arm.

Remove the steering box from the frame. We took a little bit of extratime 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 inthe center alone.

Tap on the end of the sector shaft with a rubber mallet or dead-blowhammer to remove it along with the top cap. Be prepared for a bunchof oil to drain out.


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Turn the input shaft all the way counterclockwise; youll see the pistoninside 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 abovethe piston, and remove the centering valve. (red arrow) In this picture,the box on the left is from a 1993 truck and youll notice we alreadytapped it, and the one on the right is the original 1988. Were using the1993 box, because the input shaft is longer than the 1988 version.

We moved the steering box forward, so the extra length meant wedidnt 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 acenter punch. The hole on top is more critical (and dangerous) becauseyoure drilling into an existing passageway. If you drill too far, the boxbecomes garbage. The other hole is easier, and there are two spotsyou can drill into. if youre planning on moving your box forward, dontdrill into the TOYODA stamp, because the hydraulic line plumbed tothat hole will interfere with the body mount. Otherwise, feel free to drilla new A hole. J

Drill and tap!Clean everything VERY well-you dont want metal shavings floatingaround 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, andhad custom hoses made up by Evco House of Hose. Connect the hosefrom the top of the box to the fitting farthest away from the shaft ofthe 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 everythings back together, its time to bleed the system.Bleed is a pretty accurate way to describe the process, since itseems inevitable at some point youll have red fluid spewing out of thesystem. Begin by topping off the reservoir. Start the truck and slowlycycle the steering back and forth. The fluid will become foamy. Shut


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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 valveon the top of the steering box until fluid flows out. Some boxes havethis bleeder (looks just like a brake bleeder), and some do not. If itdoesnt, 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 willbe able to turn the wheel slightly faster than the ram can react. Ittakes a little getting used to, but it is worth the sacrifice.

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