Quick rack (N13 de-powered rack) into N12

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Callumgw
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Joined: Fri Aug 11, 2006 12:55 pm
Location: Melbourne, Australia

Quick rack (N13 de-powered rack) into N12

Post by Callumgw » Tue Dec 14, 2010 8:09 pm

A Quick rack from depowering a N13 TRW Rack

NOTE: as with all these mod’s the mod’er takes FULL responsibility for the work they conduct on their own car. This work alters a steering component, which is fairly important in your car, so beware!

The assembly drawing below is for the TRW rack as fitted to the Nissan Skyline. It is very similar to the one on the N13 Pulsar. I have been told the N12 power rack has the same TRW part number as the N12 power rack. But I am yet to see one for myself…..
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These compare the standard n12 manual rack to the power n13 rack:
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What’s important is we see the lengths are the same and the pivoting locations of the rack ends are the same. This means it will not alter the factory steering geometry.

Parts Required
TRW rack from N13 Pulsar (or N12 if your lucky enough to find one!)
New tie rod ends for a N13 TRW rack
Rack bushes
Some bolts or the original line to cut and solder
Grease

These next bits are only needed if you don’t have correct N12 power one and the N13 is only needed if you don’t want to cut up you N12 one
N13 intermediate steering shaft
R31 Skyline intermediate steering shaft


Bit of background
A power rack uses pressurised fluid to assist the moving of the rack back and forth. It is metered by a torsion spring in the pinion part of the rack. This spring puts a small amount of give into the feel of the steering wheel, although I can’t say how much or how noticeable this would be. Removing this free play is thought by most to be a good idea – however it is not essential. Also, because of the internal fluid under high pressure there is a lot of seals and strength built into a power rack that are not required in a grease lubricated manual rack. Many of these seals can be removed to reduce the friction on the rack.

Time to start work

Remove the rack from the car, and start the disassembly.

Remove the boots, unscrew the tie rods from the rack. Note these parts are ‘locked’ with a swage and will be stiff to unwind.

Remove the pinion, circlips on the top and a nut on the bottom.

Removing the rack from the case is difficult. There are 4 divots near the end, drill these out. Make sure you get it all, I didn’t and things got really hard in the next step until I rectified it. With these properly drilled, it is recommended to use a pipe wrench to ‘start’ the removal. This might not be needed, but that’s up to you.
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Next hold the rack in a vice and use a drift and hammer to ‘tap’ out the rack from the other end, pushing the aluminium plug out.
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Remove the seals, including the internal seal. The internal one if very difficult, I only managed to decommission it, without managing to fully remove it. This way it won’t rub on the rack and grease can get past it.

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Remove the piston from the rack by cutting in on two sides and tapping with a chisel and hammer.
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The Pinion has a spring through the middle held to the top spline with a pin. Around that is the mechanism that meters the high pressure fluid to each side of the rack. Remove the metering mechanism by cutting under the pin shown and tap the barrel off.
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This leaves just the pinion and the internal spring.
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The following bit is optional
If you wish to remove the effect of the spring in the steering shaft, weld up this point on the spindle/pinion:
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End of optional part

Now you need to plug up or remove the holes where the power steering fluid used to pass. Welding the case is not the best idea because you can bend it and damage the operation of the rack. I managed to braze the outer hole. Unfortunately, I couldn’t braze the inner one because all the heat I put in was sucked into the aluminium centre boss of the rack. So I welded it. A simpler option would be to fill the holes with bolts.

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Similarly you can fill the holes in the Aluminium boss with bolts (if you can find the right ones), or I filled cut and solder filled the pipe and bolts from the rack.

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Cut thread for the new grub screw holes

Fully grease the rack and re-assemble.

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Don’t forget those grub screws:

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New tie rod ends
The tie rod ends from the manual rack do not fit the power rack, wrong thread. Use the ones you got with your rack or better yet buy new ones.

Installation

If you found a N12 power steering intermediate shaft – lucky you! Use that. This probably also means you have the correct rubber bushes from the n12 installation. So you’re good to go.

The rest of us, we can need to use the N13 outer rack bush and the n12 inner rack bush to mount it to the car. The N13 inner rack bush puts the rack at the wrong twist angle and it interferes with the body work and brake/fuel lines. If you can’t use the N12 one, then you’ll need to space the rack forward to get the required clearance. Just use some aluminium strap between the rack and body mounts. Don’t be tempted to use washers because then the rack won’t be held properly.

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This brings most of us to the last big challenge, fabricating a new intermediate steering shaft. Below is a collection of shafts I found at pick-a-part:

See the N13 (on top) and N12 (middle) have different fittings. The other shown (bottom) is from the r31 skyline.
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The power rack has a larger diameter spline (right image from N13), so the N12 (left in image) won’t fit it, it would also be too long because the power rack is taller. Image

The spline on the end of the N12 that mates to the steering column is bigger than for the rack (left in image below), in fact it is the same as for the power rack. The other one shown below is for the R31.
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Unfortunately the N13 spline has a missing spline to ensure correct alignment, this isn’t repeated in the N12 or Skyline splines:
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But this can be simply removed by a steady hand and the thin cutting disks that are easy to find now:
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We should be able to use the R31 universal joint and the N13 rack spline to make a correct length one for the N12. Unfortunately the diameters are not a standard steel size, so I got a piece of 20mm bar and put a 14.0mm drill hole through it. For this I used a lathe, but….you could use a drill…maybe….

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The cut the shafts to the right lengths
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fit the reinforcing tube and weld.
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Make sure you don't make it too long. if you do you'll find it binds at two points in one steering wheel rotation.

Then paint, install and GO!

C
Last edited by Callumgw on Mon Mar 21, 2011 7:01 pm, edited 4 times in total.

User avatar
Callumgw
Posts: 2354
Joined: Fri Aug 11, 2006 12:55 pm
Location: Melbourne, Australia

Post by Callumgw » Tue Dec 14, 2010 8:12 pm

15exa wrote:hop these help, kinda hard to get a good shot
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From Kane’s beautiful work we have these images of the very rare n12 powered rack for comparison to the n13 one above.
The outlet run from the side not like the n13 that run two from the front and two from the rear. So the n13 is not likely to work in a powered form....
Also the top of the pinion is a smidge lower than the n13, but not much so the intermediate shaft height is similar to the one I made for the de-powered n13.


C
Last edited by Callumgw on Sun Apr 03, 2011 4:11 pm, edited 1 time in total.

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