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Subaru Sti R180 differential and Axle conversion. (Revised)


Nizzan

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Here is a more complete write-up for the Subi diff and axle swap, and it's in it's own thread so it'll be easier to find. :)

 

If you come across a Subaru STi differential and axles and are considering swapping them into an s30 like I did, here is what needs to be done:

 

Before spending any money I made sure that this setup was even remotely possible. Because I planned on using the STi axles with the STi Diff, I knew there were no issues on the axles-to-Diff side, with splines and what not. his is because the Axles and differential are from the same year (2004) STi. I also noticed that the input flange, for which the driveshaft connects, on the differential was a different bolt pattern. But this problem can be easily resolved by simply swapping the r200/r180's input flange (from the datsun's) with that of the Subi.

 

Note: I used the r200 flange and needed to do some trimming on some of the inside dust shield in orded to prevent contact with Subi differential front seal.

 

Now there were two big issues that I came across. One: Is that the Subaru axles are about 4-6 inches to long. Two: Is that the hub side(outside part) of the subi axle has splines that go into the STI's wheel hub assembly. And I needed to somehow modify it to a flange.

 

Below:

Picture 1: is a Picture of the Subaru axle, without the end CV, going through s30 hub.

Picture 2: Is outer Subaru CV case, with 280z stub axle flanges.

100_1358.jpg

100_1351.jpg

 

So...

 

1. For the length issue, I thought, there had to be a place that made a shorter center shaft for an STI. Sure enough, The Driveshaft shop make a shorter center shaft for the STI. The stock shafts are 20 7/8". And after measuring and calculating I determined that the ideal length would be 15 1/4" to 15 1/2".

 

For my Calculations: Since I won't be using the stock center shafts, I cut them in half with the CV cases still on. Once I FINALLY cut through, I snapped in the inner half into the differential, then the outer sat into the s30 hub hole, similar to Picture #1 above. Then let the two axles cross, and then I make a mark on each one. Like this:

 

102_1766.jpg

 

EXTREMELY IMPORTANT: The center shafts of the Subaru axles have different combinations of splines on either side. I don't know why Subaru did this, but pay attention to this so you don't get the wrong center shafts. For my 2004 axles they are 30-30. Meaning 30 splines on each side. (Remember this is the spline count for the centershaft.) Other combination can be 32-34 for example. So if your ordering these from The Driveshaft Shop, make sure you know what yours are by COUNTING! Then let them Know you desired length and the spline ratio/combination/number, and your good to go.

 

As a bonus, these new shafts are built handle 400 Hp +. Now I'm just running a L30 stroker, so there is no chance I will break them. Oh I should mention these new shorter center shafts were about $400. That also includes: 4 New CV boots, 4 Tubes of CV grease, and 12 clamps. (6 small, 6 large).

 

Here the stock shaft and new shaft are side by side:

 

100_1374.jpg

 

 

2. For the other issue, the problem with not having a flange. I took the outside axle case and the 280z stub axle flange to a machinist. I told him that I wanted the spline section removed and a flange welded on to match the 280z flange. Like this:

Nizzanssubiflange.jpg

 

Notice the yellow ring on the drawing, this is used to line up and center this flange to the Stub-Axle flange. Same as the stock design. I made sure to include this with my notes to the machinist.

 

Here is some of the initial planning, with the Stock outer CV case and 280z Stub-Axle flange

100_1350.jpg

 

 

And this is the outcome, notice the outer CV case (yellow) with it's new flange welded up and painted. The red circle shows the little grooves I had to make in order for the bolts to fit through the flange.

 

100_1384-1.jpg

 

These are the axles in pieces and ready to be assembled:

 

100_1380.jpg

100_1377.jpg

100_1381.jpg

 

100_1387.jpg

 

Well once you put the new :mrgreen: CV's together your pretty well all done. Here is a picture of them in the car after about 3000 miles:

 

102_1768.jpg

 

Works flawlessly! :) The axles fit perfectly so it isn't a PITA to take out, like it was with the z31 axles. But best thing about this setup is that I got Limited Slip, the 3.90:1 gears that I wanted, both my axles and Differential have less then 20,000 miles on them, and it's lighter!

 

Price wise:

 

-The 2004 STI LSD differential with 3.90 gears. (16,000 miles) cost me about $360.

 

-Both the axles (18,000 miles) cost about $280.

 

-The new center shafts, and boots. etc. cost $400

 

-Welding/machining on outer CV case cost about $100

 

-Some POR paint and Redline gear oil. Under $100

 

While it cost a little over $1,200. Spending $700-$900 on z31 r200 LSD is sort of ridiculous. Considering how many miles there are on a 1987-1989 differential. Maybe a couple of years ago the r200's ran for a lot less than that. But I am very please with my setup. And I would highly recommend it.

 

I hope this helps those considering this swap.

 

Cheers!

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So, this is going from the stock nissan R200 to the subaru R180?

 

How difficult would you think it would be to put one in a datsun with a nissan R180?

 

Great writeup BTW.

 

EDIT: BTW how can you tell if an sti diff is lsd (i.e. ebay)?

 

For your first question, yes it is. My differentials over the time of owning the car went from the original open 3.36 r180 --> open 3.90 r200 --> Subaru "k" r180 clutch type LSD 3.90.

 

Second question; Your talking about swapping in the Subaru r180 for your original Datsun r180 in a s30?

In fact I believe it would be somewhat easier going from the stock Datsun r180 to Subi because you already have the r180 mustache bar. Also the Datsun r180 driveshaft flange should swap out with the Subaru one. So there is no issue there.

 

Third question: If it's from an STi, and it's fairly new(as in 2002 or greater) then it should be an LSD. Also it would be in the best interest of the seller to state that's it's an LSD in order to achieve maximum $ for it. So it's most likely that the seller will state it. I believe the type of LSD unit changes throughout the years. ie. Mine is a 2004 which consist of an clutch type LSD unit. In 2007+ it's a helical unit.

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  • 2 years later...

Yeah, I was thinking a nice late-model for my Fairlady Z, which has a clapped out 3.9 R180 in it now, so the Torsen setup would work nicely. And now they are 'in the scrap system'... have been waiting till I red the technical specs on the 07 STi!

Eventually it all trickles down to us bottom-feeders! :D

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  • 3 weeks later...
  • 2 weeks later...

i see thanks nizzan i actually went to a michinist and told me that he didnt even want to weld it just based on the fact of safety purposes. What he told me was that since the spline section as well as the upper part of the cv casing(bell) is hardened steel which means if he welds it then there is a high chance of it breaking due to the fact that hes bringing a hardened piece of metal and essentially making it softer. And after debating with him about this thread he anticipated that it was unsafe also due to unequal rotating mass caused by the welds. So unfortunately i need to rethink some other options for my setup. :(

Edited by nissun1
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i see thanks nizzan i actually went to a michinist and told me that he didnt even want to weld it just based on the fact of safety purposes. What he told me was that since the spline section as well as the upper part of the cv casing(bell) is hardened steel which means if he welds it then there is a high chance of it breaking due to the fact that hes bringing a hardened piece of metal and essentially making it softer. And after debating with him about the this thread he anticipated that it was unsafe also due to unequal rotating mass which is caused by the welds. So unfortunately i need to rethink some other options for my setup. :(

 

Seems you have a "Know it all" machinist on your hands. The welds are a uniform all the way around, at most being maybe x-amount of mg out of balance.... 2cm from the center of rotation.

I'm surprised he's worried about that on the axles, when there is more severity of out-of-balancing on the wheel/tire combination. Not to mention the back end of my Z is smooth as butter. But no one ever wants to be liable, which stands to reason. I had the same "safety" issue when I wanted to have a driveshaft shop weld on new universals on the steering rod. Sorry it didn't work out for you, good luck!

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yea it sucks but i couldn't even argue with a welder whom i spoke with and told me the same thing..and thats that he had 50 yrs of welding under his belt ...:( ohh well i guess i can search for another solution. Although i have no doubt your setup is rock solid.

Edited by nissun1
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For anyone who's interested in this. I had custom axles made with the STI 27 spine, Porsche axles and 240z outers. The entire setup ran me about $1200.. $1300 shipped (I got a discount because we have an account with them) and it will probably cost you $1500 at most for full retail. This would be the comparable or even better than the Beta/WolfCreek combo.

 

http://www.betamotorsports.com/products/products.php?cat=11

http://www.wolfcreekracing.com/index.php?option=com_content&view=article&id=72&Itemid=61

 

Here is what I purchased from The DriveShaftShop.. driveshaftshop.com for those who want to contact them. The whole setup is good for 700whp. Their setup is NOT listed on their page but they do this ALL THE TIME. I had to wait a month for my custom setup. But when they arrived it was pre-assembled and I am no mechanic and I was able to install these no problem.

 

IMG00144-20110512-1630.jpg

IMG00145-20110512-1756.jpg

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at the end of the day I would just get the DSS setup if you're doing a high HP application. If you're just a weekend track guy and don't demand high performance I'd do the Beta stubs with stock axles. I'm sure the driveshaft shop can do a lesser setup. He told me they have a 300hp version for about $700 I believe.

 

I hope this helps you folks out there

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