Subaru STi Differential Identification

[Black Pearl]

Hello all, 

 

I'm doing a STi limited slip differential swap into my 1978 280z, and I was wondering if someone could help me identify my STi differential.  I was told it was out of a 2008 STi which would make it a 3.54 gear ratio with a Torsen limited slip unit, correct?  I cannot find the gear ratio stamp on the ring gear where others have shown it located.  Also, does it look like it has the Torsen LSD unit?  Any help is appreciated!

 

 

 

 

 

 

Thanks,

Keaton

[Mike C]

It is a limited slip of some sort with the 2 piece case based on the seam on the ring gear flange. It looksl like it has helical gears like a Torsen to me. I've never seen a ring gear that didn't have anything stamped on it, so rotate it around and look for markings where that yellow paint mark is now. Otherwise, with the the cover off, count the teeth on the pinion gear and count the teeth on the ring gear. Divide the pinion into the ring and that's your gear ratio.

[mrcheeze36]

Torsen but an 07' is 3.54 and an 08' is a 3.9:

http://forums.hybridz.org/topic/38251-complete-differential-list-need-help/?p=681962

[Black Pearl]

I appreciate all the help.  I counted the teeth and came up with the 3.545 ratio.  I could not locate a stamp anywhere on the ring gear..

 

Thanks!

Keaton

[mrcheeze36]

If a 3.54 with a Torsen, then it's off of an 07'.

[jmhtx]

I've got a R180 off a 2008 STI.  The gear ratio is lightly stamped on the ring.  It is very difficult to see, but it is there.  

 

[matthewabate]

I’m really sorry to revive a dead thread, but I thought it would be better than starting a new one and can’t find the info I’m looking for.

 

I have a differential that was supposed to be out of a 2014 WRX STi, but it turns out it is an open dif, so probably a regular WRX. I did the usual test where you turn the input and hold one axle and the other one spins. I don’t think my bare hands are applying enough torque to overcome the mechanism, right? So it’s open.

 

I bought a carrier from Japan that is supposedly an STi Torsen LSD. When I opened the case they look pretty much the same (with different numbers stamped and cast into them).

 

So either I got taken twice or I’m not understanding something.

 

Can anyone point me to a resource for using the numbers to identify the carrier? I saw a thread way back that showed every Subaru carrier and talked through the differences, but I can’t find it now.

 

Alternately, can anyone tell me how to make sure the loose carrier is an LSD without having axles in it?

Edited November 26, 2023 by matthewabate

[AydinZ71]

An open carrier and LSD carrier assembly can not be mistaken for one another. Google “open diff”. They look like four gears arranged in a square, one engaging the other. 
 

an LSD carrier will be a cylinder with inspection holes arranged periodically around it. You will not see the same type of gears inside.

 

a Torsen/helical does have gears inside the cylinder, but they look nothing like an open carrier. Google is your friend here, again.

 

the shaft spin test does not work the same way between a Torsen (14’ STI is one) and a clutched unit (OS Giken, 05-07’ STI). The clutch type requires differential torque to overcome the clutch. A helical is the opposite. It requires significant input shaft torque to resist each side from spinning independently.

 

sounds like you may have two Torsen carriers 

 

 

Edited November 27, 2023 by AydinZ71

[jhm]

@matthewabate, here's a couple threads that should help you ID which diff you have. 

 

https://forums.nasioc.com/forums/showthread.php?t=2597453

 

https://forums.hybridz.org/topic/105868-subaru-diff-clarification/

 

You can determine your diff type on inspection; and I suspect that @AydinZ71 is correct in his last line supposition.

 

Hope this helps.

 

[matthewabate]

Thank you both. Yes, I have two Torsens, verified by the pictures in the spotter’s guide.