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Been working on power steering. I decided on a 2004 Subaru WRX steering rack.
 
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I did some measuring to make sure everything would work. First I needed to figure out how much to cut off the steering rod. In steering, the pivots are the key to getting it to handle correctly. The stock pivots on the 240z steering rack is 616mm. The WRX rack is about 634mm. Some individuals use older Celica inner tie rods with the stock Subi outers to get everything to fit, but my rack is the "late" Subi rack. The threads are larger, M16 x 1.5, on the "late" Subi rack and the Celica rods didn't fit. I did some online research and found that 2000 Hyundai Sonata rods had the correct length and thread. The added bonus is that the inside of the Hyundai rods are vented and stepped to allow for more steering angle without shortening the outer tube of the steering rack. The step did have a lip that had to be ground down though. The step on the Hyundai rod is 5mm which adds 10mm on the travel on the steering. So, while I cut 18mm of the rod, it reduced the travel by 8mm. Stock 240z travel is 120mm, Subi is 132mm. Now the travel is around 124mm because the measurements are not perfect. So I added a little travel, hopefully it doesn't bind the steering knuckles. Here is a picture comparing the shortened Subi rod vs. the 240z rack. The final measurement was 576mm for the steering rod.

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Then I mounted the subframe on the engine to check clearances . In this swap, the engine mount perch has to be clearanced to make room for the angle of the Subi steering shaft.

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Also, the subframe has to be clearanced for the rotary valve and lines.

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Also checked the clearances with the A/C compressor mounted and to plan the pressure line.

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I cut the end of the steering shaft off to weld the Subi U-joint to the 240z steering shaft. I just shaved the weld and pulled the shaft out the Subi joint and the 240z shaft diameter was exactly the correct diameter to push inside and weld. I think it looks better that the stock Nissan weld, and that lasted 45 years. Hope I didn't cook the grease out of the joint when I welded it. There wasn't much smoke, so I think I am good.

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The stock Subaru rod ends ended up only having about 12mm of thread engagement when the alignment was roughed in and I wanted more. I did some research and figured out that 2003-2009 Mazda 6 tie rod ends are 7mm longer than the WRX ends. They are curve and have a left and right though. The taper on the stud seemed to match the original Datsun rods as well. Now I have plenty of thread engagement.
 
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I used compression fittings to move the hydraulic lines to where they would fit around the subframe. They worked out well and only one needed to be tightened up. They are 1/4 inch fittings.
 
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This is how much I had to cut out of the subframe. Metal was added to strengthen the subframe. If the engine mount becomes a problem, then I will gusset it.
 
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I used the RB25 (R33 non HICAS) pump, which is the same as most 240sx pumps. I built the pressure line out of -6AN Fragola PTFE hose with a M16 x 1.5 banjo metric adapter and the M14 x 1.5 power steering fitting for the rack. I did kinda skimp on the reservoir though and will switch it with an OEM style later. I used a 120 degree end on the rack side so it will clear the A/C pump later. Should have used a 150 degree though.
 
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The feel is great and feels about as a power steering car should. I dont have too many bumpy roads around here, so I cant fully test for bump steer. Havent felt any yet and we do have some railroad crossings that I have tried. There arent too many curvy roads either, but parking lots seem to be way more tolerable. The steering ratio seemed to stay about 2.7 and without a degree wheel to measure it, will stay "about".
 
If there are any questions, let me know and I will ad them in the first post to help keep everything together. 

Edited by winstonusmc

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Not sure, seems a lot of the Suby stuff is the same. The only difference seems to be in the years, which is the larger tie rods in the later years.  The write up I read was dealing with older GC chassis WRX, and my rack is from the GD chassis. Not sure how they cross with the Forester. I found more Impreza racks on Ebay anyway.

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The rack ratios are different in forester and Impreza vs wrx vs sti. The 2004 sti rack is the fastest rate but is otherwise externally equivalent to the WRX rack.

 

If I remember right the sti is 2.5 turns lock to lock. The wrx is 2.7, and the forester/Impreza are 3.something. The inner tie rod threads changed from m14 to m16 somewhere around 2000model year, and the splines on the input changed as well from a Subaru proprietary spline to a common pattern.

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Been a lurker here for a while sponging Z information from this great forum/community. But coming from the land of subaru, I finally might be able to give back some info here.

 

Pre 05 Impreza racks (including WRX) are 16.5:1 ratio and 3 turns. They also share the same mounting (so interchangeable to the crossmember at least).

 

The 04 sti rack is 15.2:1 ratio and 2.7 turns. Shares the same crossmember mounting as the pre 05 impreza and WRX.

 

The 05 thru 15 WRX and STI racks are all 15.2:1 and 2.6 turns. The difference in turns (2.7 vs 2.6) is believed to come from a new limiter because of a change in wheel widths. New crossmember mounting started in 05, and changed again in 11.

 

The 03 to 08 Forester rack is a variable rack with 19.1:1 ratio at center and 15.2:1 and the ends, and 3 turns. Same mounting as the pre 05 impreza, WRX, and STI. Unsure of the pre 03 Forester racks.

 

 

Hope this helps a little.

Edited by PlanetGranite

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It would be more meaningful to compare the racks based on the rack movement per revolution of the pinion.  For instance the 240Z rack moves 1.81 inches per revolution,and the later 260Z and 280Z racks moved 1.59 inches per revolution.

 

I like the idea of power steering, but I also want a rack that is shorter than the S30 rack (center to center of inner tie rod pivot points).

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The Subaru racks are all the same length and interchangeable with each other (excluding tie rod threads, input splines, or 2005 housing-crossmember attachment method)

 

Nasioc boards has tons on resources on similar interchangeability.

 

The Subaru racks are all longer than the Z rack.

 

Some resources here:

http://forums.hybridz.org/topic/46504-lt1-and-subaru-rack/

Www.vikingds.com/zcarguy/power%20steering%20install.pdf

Www.viczcar.com/forum/topic/5387-240260-power-steering-options-Subaru-vs-mx5/

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