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Subaru WRX STi R180 Side Axles


johnc

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Seems to me, using that material, even with half-assed heat treatment, the weld is going to be the weak spot, not the splines. How are you addressing that? (seriously interested, since I am studying to be a metallurgical engineer)

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Seems to me, using that material, even with half-assed heat treatment, the weld is going to be the weak spot, not the splines. How are you addressing that? (seriously interested, since I am studying to be a metallurgical engineer)

 

Through design, process, and testing.

 

In any manufactured part there is going to be a weak spot. The factory side axles have the flange fusion welded to the axle the same as the factory stub axles.

 

There are two welds holding the flange onto the axles and both have .063" 60 degree bevels machined into the welded joint. ER70S-2 filler is used and the parts are TIG welded. We did not use ER80 filler because of the post welding carburizing. The additional carbon content of ER80 would have made the surface carbon content at the weld too high after carburizing.

 

We're designing for a 2,500 lb. 240Z making about 275 ft. lbs. of torque running 275 width wheels. Which is almost exactly what the Rusty Old Datsun was back when I ran R180s behind it with Quaife diffs and stock side axles.

Edited by johnc
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BTW... we are investigating makes the parts one piece instead of having a welded flange. My original idea was to make one axle and separate flanges for that various CV shafts and halfshafts could be adapted to the STi diff (thinking beyond you 240Z guys.... :-) )

 

But that idea probably is too complicated and it might end up cheaper just to have a different machining program for each particular adapter.

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Hi John, the 2006 STI should be CLSD also (like the 04' and 05').

 

3.54 ratios are in the 2006 and 2007 STI.

3.90 ratios are in the 2004, 2005, and 2008 STI.

Torsen LSDs came in the 2007 and 2008 STI.

 

Does anyone have a link to a list of all of the Subaru Differentials?

 

Ratios, spline count, etc?

 

My boss has several Impreza/Outback parts cars and I can take whatever I can use.

 

Sorry for going off topic John, I was hoping I could buy a set of these and have a diff already waiting for them.

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I need to point out one thing here. The 240Z uses a 25 spline output shaft and the 2006 STI uses a 27 spline output shaft. The WRX uses a 25 spline, but, this WRX version is not as beefy as the STI LSD. I'm not sure, but I thing the late-model 280Z uses 29 spline.

 

Someday we will have a 240Z / STI, but I ain't holding my breath.

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So... you don't want to test these for me Bob? I had you on the list but I can use someone else. Please let me know.

 

I do want to test these for you. We're hoping to be at Buttonwillow in October with the Alfa Club. http://www.aroschpd.org/

 

ATM, we are in the process of installing all new neoprene bushings, shocks and springs. Front is done, rear is almost done. While the stock diffy was out we tried to fit the stock axles into our STI LSD and found it won't fit because of the spline count. We knew it wouldn't work because of the bolt-in VS snap-in style, but were surprised to find a spline count difference.

 

From here I tried to buy some used WRX axles (taking my LSD with me) to find that the WRX did not fit our LSD. The seller was doing a STI upgrade to his WRX and let me try his STI axles which did fit.

 

Our LSD is an 06 STI clutch type with 27 splines. Subaru also uses a Viscus type which probably won't take any real abuse. Both look the same on the outside and are a direct bolt-in to the 240z (except for the axles and drive-shaft). Yes, there is a difference between the WRX and STI drive-shaft.

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Yes, I'm aware of that difference between the WRX and WRX STi R180 differentials. That's why I'm building these shafts. They will have a 28mm OD, 27 spline, snap ring shaft welded to a four bolt flange that will allow bolt-up of the stock 240Z halfshafts.

 

The prototypes are getting final machining this weekend then they go to the broacher to get the splines cut. After that they got out for carburizing and then a final inspection. I have not sourced the proper M10 x 1.25p studs new (damn hard to find actually) so I'm going to install some used ones from the dozens or side axles I have on a shelf.

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I called around yesterday and found the last 12 of the factory Nissan D head studs here in the US and the dealer is checking to see if they can order a bunch more for me from Japan. FYI... list price from Nissan on these studs is $6.08 each!

 

Unfortunately these are a unique length (23mm) and the shoulder is 10.5mm.

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