Subaru Rack Size Compared to Stock Z Rack

[tonycharger72]

Hey guys,

 

Just thought I would share some measurements I took of my Subaru Rack and Stock Z rack, I have searched through this forum and have looked at other peoples measurements of the Z & Subaru racks, the measurements given for the Subaru racks were very close to mine but think peoples measurements of the stock Z rack was a touch off.........

 

The reason for this was when I mounted the Subaru rack on an original Z crossmember with the JTR bumptsteer mod (3/4" up and 1/4" out) that the end of the Subaru rack seemed to sit inside the LCA pivot point - thought this was weird,

 

So I pulled apart the Z rack and pulled apart the Subaru rack and this is what I came up with - very very close in size!!!

 

In fact, the stock Z rack is actually a touch longer than the Subaru Rack!!!

 

This rack was from an early 90's Legacy,

 

[big-phil]

is this for converting to power steering?

[260DET]

There may be interest in what size and hand the tie rod threads are, if that has not already been covered.

 

I know that 280ZX tie rods are sometimes used with stock S30 racks where front track has been increased by pushing out the LCA pivot points. Apparently they are both RH threaded on the 280ZX but the bit out of the end of the ZX rack will swap into the S30 rack to replace the one which is left threaded.

[tonycharger72]

Yes it is for Power Steering,

 

I have been doing some more measuring after a fellow member prompted me to look at where the rack-ends (inner tie-rod-end) pivot points were for the respective racks,

 

Not good news it seems...............

 

The Z rack-ends sorta screw over the top of the end of the rack, whilst the Subaru rack ends screw into the end of the rack as shown here,

 

 

If you place the Z rack on a stock crossmember the rack-ends, once screwed property into the rack, locate the pivot of the rack-end in line with the LCA pivot hole on the crossmember,

 

However, because the Subaru rack end has a different fitting for the rack-ends and they screw into the end of the rack, not sit over the top of the rack like the Z rack-ends, the pivot of the rack end effectively sits about 17mm or so further out than the pivot point of the Datsun Z rack,

 

This means that to maintain proper geometry you really should be moving the LCA pivot point out around 15-20mm when installing the Subaru Rack,

 

 

That could cause some issues

 

Only way around this would be to find rack-ends that fit into the Subaru rack with much smaller housings for the ball pivots so as to bring back the pivot point to as close to the Z pivot points!!!

[JMortensen]

Would it be possible to turn threads farther down the shaft and cut the excess off?

[tonycharger72]

Would it be possible to turn threads farther down the shaft and cut the excess off?

 

Possible,

 

But its just a hollow tube, so cant just drill a longer hole and tap it unfortunately, I stuck a scew-driver in the end of the Subaru rack to illustrate,

 

 

EDIT:

 

It appears as if Jon's suggestion would be a goer for this conversion,

 

The Subaru rack is hollow as shown above and is threaded at the end for about 10-15mm, it appears as if the tube diameter is slightly smaller once you go past the thread, which would infer that a thread was just cut to suit the length of the rack-end threads!

 

Therefore, cutting the end of the Subaru racks and running a thread inside the tube should work out!

 

The rack pictured is just a dummy rack, so not to fussed if I make a mess of it, I will cut the end of the rack and see if I can get a friend to run tap (as I don't have any) in the Subaru rack,

 

Will post the results as soon as possible!

[mark]

I drilled out and tapped my subie rack to accept the Datsun inner tie rods.

[tonycharger72]

I drilled out and tapped my subie rack to accept the Datsun inner tie rods.

 

How is that possible?

 

Subaru rack is a hollow tube, what did u drill out?

 

What Subaru rack did you use? you use Z rack-ends or another Datsun???

 

Z rack-ends (inner tie rod ends) are of a completely different design and thread over the top of the rack end, not into it like the Subaru..........you wouldnt be drilling anything out to accomodate the Z inner tie rod ends mounting to the Subaru rack, you would be putting a threaded collar onto the Subaru rack to except the female thread of the Z rack-ends................which would be equally as tricky as the Subaru rack tapers at the very ends as seen in the above pics................

 

More information mate ?

[mark]

I used inner tie rods from a 280zx power rack and the outer tie rods from a Z, both were the right hand threaded tie rod ends. I had to increase the diameter of the subie rack (from on 04 sti) adn rethread to accept the 280zx inner tie rods.

 

How is that possible?

 

Subaru rack is a hollow tube, what did u drill out?

 

What Subaru rack did you use? you use Z rack-ends or another Datsun???

 

Z rack-ends (inner tie rod ends) are of a completely different design and thread over the top of the rack end, not into it like the Subaru..........you wouldnt be drilling anything out to accomodate the Z inner tie rod ends mounting to the Subaru rack, you would be putting a threaded collar onto the Subaru rack to except the female thread of the Z rack-ends................which would be equally as tricky as the Subaru rack tapers at the very ends as seen in the above pics................

 

More information mate ?

[tonycharger72]

I used inner tie rods from a 280zx power rack and the outer tie rods from a Z, both were the right hand threaded tie rod ends. I had to increase the diameter of the subie rack (from on 04 sti) adn rethread to accept the 280zx inner tie rods.

 

My Rack is early 90's Legacy, but from all the Subaru Racks I have seen from 90's Subaru's and other members racks on Hybridz they appear very similar, 2004 is very late model though, might be more meat on the ends?

 

Any pics of the rack, the 280zx inner's installed?

[mark]

I pulled the boot back to get a shot for you.

 

Drilled and taped to 16x1.0 to fit the 280zx inner tie rods.

 

[tonycharger72]

Awesome mate, thanks for going to the trouble!

 

Well done on the conversion too!

 

So with the 280zx inner's and Z tie-rods you were able to replicate the length of the original Z inner's and outers?

 

And by cutting and re-threading the rack you were able to correctly align the rack-end pivot points with the LCA pivot points?

 

One more thing concerns about me about this swap (any PS swap actually), is being able to limit pressure at high engine speeds, I know there is that Heidt pressure valve, but its manually operated, ideally would like to have it automatically controlled - has anyone who has done this swap (or any PS swap) managed to automatically via mechanical or electronical means alter the PS fluid flow through the engine's RPM range?

[ezzzzzzz]

I used a STI rack (2001?). It is longer than the Z rack. I had .5" removed from both ends, drilled and tapped (something like 16-1.0) to accept 2000 Volvo S80 outer tie rods. There are specific tools needed to dismantle and reassemble a Suby rack to prevent damage to the seals. I have those tools after some searching and lucky deals (they are stupid expensive). Let me note one thing for certain. You MUST get the model, VIN and build date from the donor vehicle. Suby uses a dozen or so different seals and none are marked. Their parts counter person will be useless without that info to get proper replacement parts. You may find seals at the local bearing/seal supply if they can get good dimensions though. There are extensive write-ups here about it. I haven't gotten any further with the upgrade as other things have taken precedence.

 

Tony, all PS pumps have a built-in bypass to prevent excessive pressure.

[tonycharger72]

I used a STI rack (2001?). It is longer than the Z rack. I had .5" removed from both ends, drilled and tapped (something like 16-1.0) to accept 2000 Volvo S80 outer tie rods.

 

Sure it's longer than the Z rack or because the tie-rod end design is different and screws into, not over the end of the rack like the Z rack-ends that you percieved it to be a different length,

 

Like this...............this is flat out wrong, the Z rack is longer, not shorter than the Subaru rack!!!

 

 

And until I measure my own racks I to believed the Z rack was shorter than the Subaru rack when in fact its a fraction longer!!!

 

Also, this picture appears to illistrate how most folks have gone about completing this conversion, not worried at all about where the inner pivot points line up in regards to the LCA pivots, all seem to have just focused on getting the overall length correct!!!

 

There are specific tools needed to dismantle and reassemble a Suby rack to prevent damage to the seals. I have those tools after some searching and lucky deals (they are stupid expensive). Let me note one thing for certain. You MUST get the model, VIN and build date from the donor vehicle. Suby uses a dozen or so different seals and none are marked. Their parts counter person will be useless without that info to get proper replacement parts.

 

I had the exact same experience in Australia , the fellow behind the counter couldn't tell me a thing, I literally had to go back to the wrecking yard and grab a VIN number!!!

 

ezzzzzzz,

 

On the ends of the Subaru rack where the rack-ends thread in, originally there is a locking washer installed, if you cut the end of the rack you also cut off the locating nubs on the end of the rack for this washer to locate itself and completely secure the rack-ends in place - did you do anything about this or just use Locktite or something on the rack-ends into Subaru rack threads??? Local Subaru mechanic said he often found it tricky to get in those special little washers and usually ended up having to use Locktite instead!!!

 

There are extensive write-ups here about it. I haven't gotten any further with the upgrade as other things have taken precedence.

 

I disagree with this one, sure there is a "sticky" with lots of great information, but until posting this particular thread I had absolutely no idea that people had cut down and re-threaded their Subaru racks so as to properly align the LCA pivot point,

 

Also, there is a great deal of random parts used,

 

1. Stock Subaru rack ends, cut down and re-threaded to use 90's Corrolla Tie-Rod ends and then reaming the Z steering knuckle to except the Tie-Rod, however you drop from a 14mm to 12mm thread to except the Corrolla rack ends!

 

2. Late 80's Celica Rack-ends and stock Datsun Tie-Rod ends,

 

3. S80 Volvo Rack ends and modified Z tie-rod ends, I may be wrong but 78Zlt1 does not appear to have modified the Subaru rack in any way at all............

 

I did some work on my rack after hours of searching I found these parts that seem to work.

 

TIE ROD INNER Volvo S80 01-05 part # 274179

These have the same inner thread as the subaru and the correct outer thread for the stock datsun outer tie rod.

They do need to be slightly modified as seen in the photo. top is stock bottom both ends are cut down a bit, the reason they have to be shortened is they would otherwise bottom out.

 

 

The stock datsun tie rods also needs to be shortened slightly.

Top is stock , bottom is modified version.

 

 

4. From my own investigation and inability to attain S80 Volvo ends, I got hold of some S70 Volvo rack-ends which thread perfectly into the Subaru steering rack and leave about 13cm's of room for a tie-rod end, they had a very course thread though, from memory different from the Z tie-rod ends,

 

5. 280zx's inners and stock Z outters,

 

BUT.............from reading through what other members have done I really haven't gotten the impression that anyone ever bothered with trying to align the Subaru rack-end pivots and the LCA pivots??? Maybe I wasn't reading closely enough! And there is some pretty random old combinations going on there ,

 

Sure everyone isn't using the same exact rack, I have a 1991 Liberty and a 1994 Legacy (they appear identical), but from looking at pics of other's racks and the different year's and model Subaru's they came out of they look awfully similar to mine!!! Maybe the later Subaru racks are completely different, they are certainly a lot more expensive , but they all look pretty dammed similar!

 

 

Tony, all PS pumps have a built-in bypass to prevent excessive pressure.

 

So no matter how fast your engine is going your pump doesnt just keep spinning and pumping out higher and higher volumes? it stays at a constant pressure no matter how fast the engine is going?

 

Why would you need a product like this then? Guess it is for really old PS pump's without that particular feature or if you just want to change the feel of the factory setup?

 

http://www.heidts.com/index.cfm/page/ptype=product/product_id=210/category_id=88/home_id=88/mode=prod/prd210.htm

[ZZZeee]

This information should be organized and moved into an existing sticky.

[tonycharger72]

Sorry, if I didnt not make myself clear before, but I assume, like ezzzzzzzz said, that almost all PS pumps have a limiter in them that keeps pressure at a given rate, like 2 gallon/minute (whatever, figure is a random number), but not entirely sure you want this constant pressure when at high speeds - what I am after is "VARIABLE FLUID FLOW"!!!

 

But after reading through this, it appears it has been standard kit on cars for 20years , BUT...............they don't always just mount them on the pump and they don't all appear to be mechanically controlled!!!

 

http://www.aa1car.com/library/2004/bf10434.htm

 

Illustration on the page (couldn't get rid of the 2nd pic sorry )

 

 

.window.google_render_ad();

 

 

Some units use an ECU to limit/increase the fluid flow, the GM appears to use Magnets on the rack with it's "MagnaSteer" setup, whilst Ford T-Bird uses a valve on the pump,

 

Hhhhhhhhmmmmmmm, think it wouldn't be a stretch to assume that not all pumps have a "variable fluid limiter" in built in them, as it appears some manufactures have used other means to limit fluid volume from the pump, via ECU, things on the rack, magnets, etc, etc, think with the Subaru rack slapped into the Z you would need to use a specific pump to gain this feature!!!

[cockerstar]

But there is no issue with pressure and flow when using the stock Z pump and the subi rack, correct?

 

I'm very interested in this swap and it's definitely going on my list of things to do when refreshing my suspension in the future

[tonycharger72]

But there is no issue with pressure and flow when using the stock Z pump and the subi rack, correct?

 

No such thing as a stock Z pump, PS didnt appear until the 280zx, and highly doubt the 280zx does anything more than supply "X" amout of fluid, I may be wrong, but doubt it is variable.............

 

Went out to a mates house and cut the end of the Subaru Rack and basically extended the threaded down 15mm - did this by placing the tap into the existing thread before we cut it and cut the new thread, then hacked 20mm of the end - there is a hot spot on the spine of the shaft, so hack-saw couldnt make it the whole way through, had to use the angle grinder - touch crude

 

 

Bit of a lousy pic (camera phone, 5mg my a#s , but this is the new thread cut!!!

 

 

This is a pic of the stock Subaru Rack-End installed onto the Subaru Rack,

 

 

The other side is a little bit more complicated, there is a taper in the Subaru Rack Shaft, however there should still be enough meat in the Subaru shaft to run a 14mm thread - narrows from 23mm to 20mm approximately!!!

 

I have put the Verniers to show 35mm, this would be the 20mm you cut off the end of the rack and further 15mm worth of thread required to fully seat the Rack-End you would use!!!

 

 

This is a pic of the Subaru Rack ends, Datsun Rack-End with Z Tie-Rod-End and Z Tie-Rod-End on its own, this shows that there really isn't enough room to be cutting down the stock Rack-End so you could run the stock Z Rack-End!!!

 

 

This pics shows where the Subaru-Rack-Locating washer sits in the end of the Subaru Rack, once you cut 20mm of the end of the Subaru Rack you lose these ears, however don't think it would be to much trouble to cut the end of the "new" shorten rack to include these "ears"!!!

 

 

I think it would be important to be able to retain the stock Z outter Tie-Rod ends because they are a pretty weird shape, NOT STRAIGHT, if you werent able to use them I would be thinking this conversion might be a touch dodge.......................anyone else got an opinion on that one?

 

NOTE: REALLY REALLY IMPORTANT, no one go out and hack 20mm of the end of their Subaru Rack just yet , until I find the appropriate Rack-End, which may have a different sized housing and therefore locate the pivot point in a slightly different position, which means less than 20mm would be required to lop of the end of the Subaru Rack!!!

 

Therefore, need different Rack-Ends, so have to get my hands on some S80 Volvo or 280zx or late 80's Celica and see what they look like bolted together, more to come!

[mark]

Awesome mate, thanks for going to the trouble!

 

Well done on the conversion too!

 

So with the 280zx inner's and Z tie-rods you were able to replicate the length of the original Z inner's and outers?

 

And by cutting and re-threading the rack you were able to correctly align the rack-end pivot points with the LCA pivot points?

 

One more thing concerns about me about this swap (any PS swap actually), is being able to limit pressure at high engine speeds, I know there is that Heidt pressure valve, but its manually operated, ideally would like to have it automatically controlled - has anyone who has done this swap (or any PS swap) managed to automatically via mechanical or electronical means alter the PS fluid flow through the engine's RPM range?

 

 

The pivot point on the tie rods and the control arms are even. The car has been on the track for a couple of years. This mod has done exactly what I expected it to do, allow my skinny arms to turn 285's with ease.

The car handles amazingly well.

 

The only problem I had was I burned up the stock ls-1 power steering pump after 2 or 3 track days. This place was the answer.

 

http://www.turnone-steering.com/pumpdirectory.html

 

Good luck with your conversion.

[ezzzzzzz]

Well, I can only speak for myself with this conversion. I measured a spare 240Z rack against the STI rack (not the housing, not the whole assembly but just the actual rack). There was a difference between the two (the Suby was longer at the tie rod pivot points). This rack material is very hard. I had a machine shop cut .5" off each end. The hole was drilled deeper and tapped further to use the S80 tie rods without having to cut those shorter. I did this to ease tie rod replacement later on. The slots for the locking tabs were also machined into the rack. NOTE: This machine work placed the pivot in the S80 tie rods at the original location of the stock tie rods. I can only speak for the 240Z rack and the Suby rack I used. There is likely to be differences between years and models of both makes. Unlike others, I didn't give a crap about the overall length as the S80 tie rods allowed for appropriate adjustment with plenty of thread. I know I'm missing something here as it's been nearly a year since I started that project.

Heidt's PS gear is race oriented. I was referring to OEM production parts. I should have made myself clearer. Yes, there are newer systems that provide variable pressure that is speed dependent. It becomes complex and expensive I'm sure. It also is probably computer controlled. The boundaries are endless for modification and modernization. I have found that compromise works well for me. It comes down to $$$. To a point, many improvements can be made. After that, the return becomes expontentially smaller. I'll post some photos tonight of my setup on the bench.