Hydro assist can be broken down into six components: the pump, steering box, ram, hydraulic lines, reservoir, and inline cooler.  Yotas and Jeeps have the luxury of bolt on kits.  For us with Nissans, however, we have to piece our systems together and do a few modifications.  But, in the end you’ll have a good setup for much less than the cost of a complete bolt on kit.

First, adding hydro assist typically requires a modified or higher performance  power steering pump to help feed the hydraulic cylinder.  Without an increased flow rate from the pump steering will feel sluggish and delayed.  Luckily, for us with early model Nissan Pathfinders and Hardbodys, our pumps are easily modified by drilling out the restrictor plug, which is pointed out to in the 1st pic.  Remove this and open up the center hole with a 5/32″ drill bit.  If you have a 91 or later Nissan you may have to swap it for an older model year pump, as the newer pumps use a different regulator design and are not easily modified.  The 2nd pic shows a comparison of the two styles of plugs  and their regulator assemblies with the newer one on top.  Fortunately, everything else about the two pumps are identical, thus making it a simple swap.  Finding one at your local wrecking yard should not be, too, difficult.

Next, you will need to drill and tap the steering box for two 1/4″ NPT hydraulic adapters (click).  To keep the metal chips out of the system it is best to completely disassemble the box before drilling the case.  This is a straight forward task if you keep things in order.  click here for a great site showing a box being torn down and tapped. One important note on older 90’s and earlier boxes is that the needle bearings surrounding the sector shaft are not caged.  So, keep track of them as the individual bearings fall out when you remove the sector shaft from the case and use a little grease to hold them in during reassembly.  Another method is to use a thin plastic sheet (a clear portfolio cover has worked for me)  to wrap around and slide in between the sector shaft has you pull it out, thus pushing out against the needle bearing and holding them in place.  This is better illustrated in the Nissan Factory Service Manual.   From the next two pics you can see where the two ports need to be placed.  One hole needs to tap into the vain that runs along the top of the case.  This vain feeds fluid to the front of the case, pushing the worm gear assembly back and turning the pitman arm to the left.    Locate the other hole as best you can tell in the pic.  The exact location is not critical as you are tapping into the large cavity containing the sector shaft.

Ported 1991 Nissan Pathfinder steering Box

With the box ported, next you will want a 2″ bore, dual acting ram with the proper stroke for your axle–6.5″ stroke for a Dana 44.  Longer strokes will work fine, too. Just be cautious when turning to full cut as a longer stroke ram will want to push the knuckles and steering box past your steering stops.  So, make sure your knuckles or steering box are set up to take the abuse.  The next pic shows a 2″x8″ ram (click) mounted on a Dana 44.  One side is mounted to the axle, typically on the diff cover, and the other side mounted to the tie rod.

Now, which hydraulic lines you need will depend on what fittings you have coming off your ram.  If you go with the surpluscenter ram pictured above (here), then, you will need two SAE 8M to JIC 6M adapters (here).  This will match the JIC 6M fitting you installed on the steering bock.  Get two 3/8×36″ hoses (here) and your ready to hook them up.  Just remember the line going to the top of the box will need to turn the wheels left.  With the ram oriented like in the pic above, this line will go to the passenger side port.

With the modified power steering pump generating more heat, an inline fluid cooler is critical.  Any 10,000 pound GVWR oil cooler should do it.  Just run it anywhere in-line with the low pressure power steering hose.  Lastly, the added displacement of the hydraulic ram will cause fluid to spill out of the stock reservoir.  So, you want a reservoir about double the capacity.

That covers all the parts to running hydro assist.  To summarize:  1) you need to drill out your existing power steering pump, 2) drill and tap the steering box, 3) mount the hyrdraulic ram, 4) run hydraulic lines from the box to the ram, 5) use a higher capacity fluid reservoir, and 6) add an in-line fluid cooler.

Full Story: Nissan Pathfinder Hydro Assist Steering

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