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How exactly does the LSD work?


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8 replies to this topic

#1 springer-

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Posted 04 March 2013 - 09:13 PM

I know what a LSD is and I know how some of them work in terms of when they apply power to the rear wheels but I would like to know how the Subaru one works.

 

I am looking for a later model rear with a LSD in it for a 85 GL ea81 off road project.  Some LSD's "release" at speed or for cornering or at lower speeds as I understand it??  Sine I am looking for a 4wd offroad application I am wantng something that grabs and applies power to both wheels but has give when cornering.  Is this what I should expect from a stock rear with LSD or does it operate differently since it is designed for street use mostly?

 

Thanks



#2 monstaru

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Posted 04 March 2013 - 09:38 PM

FAQ in the "offroad" section.
Read, LOVE , LEARN.

#3 springer-

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Posted 04 March 2013 - 11:03 PM

Ok so pretty much what I expected however that brings up more questions.  Does it suggest all the LSD's after 91-ish are VLSD's?  Are all the "inny" rears VLSD?  I wanted change out to a later "inny" rear.  Would the VLSD work better than the clutch type in my application?



#4 1-3-2-4

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Posted 05 March 2013 - 12:41 PM

The clutch wears out plus I don't think Subaru stocks them anymore? The vlsd is just that viscous fluid that gets sheered when the rotation speed is more than the other side.. the faster the spin the quicker to react.. stock vlsd is pretty weak and takes a a few almost 100 tons to get the transfer to start

#5 nipper

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Posted 05 March 2013 - 09:09 PM

You cant really swap from a Viscous coupling to a clutch type as there isnt enough room there I think.

 

Clutch type LSD rock, but they are heavy and with small engines can be a power robber. Viscous couplings work by having plates with multiple holes and are filled with silicon. Silicon is a funny fluid as when it heats up it gets thicker and acts like a clutch. It is lighter ans simplier then a clutch type, but does have a delayed reaction time, which is not always a bad thing. The reaction time is set by the plates and holes in the plates. As soon as everything catches up to speed the fluid cools off and flows again. There is a mechanical diff that can be swapped in (housing and all) but it is a very rare find.



#6 springer-

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Posted 06 March 2013 - 09:24 PM

I was looking at possibly going with a "Suretrac" LSD.  But from what I read if one tire is off the ground the other doesn't get power .... in the same article it states that when one starts to slip it applies power to the other wheel.  Seems like a contradiction to me ... isn't one wheel off the ground like the ultimate slipping tire?  Wouldn't that transfer the power to the other wheel even better?

 

Thanks for the replies.



#7 nipper

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Posted 06 March 2013 - 09:56 PM

It is, that is it's strength and weakness. it is made for performance traction not to get you unstuck

 

These are center diffs 

 

http://www.autozine....ction_4wd_2.htm

 

 

These are rear diffs, start about page 4 if you know the basics already

 

http://auto.howstuff...ifferential.htm



#8 Gloyale

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Posted 07 March 2013 - 12:23 PM

You cant really swap from a Viscous coupling to a clutch type as there isnt enough room there I think.

 

Internals of all the r-160 rears are interchangeable. you can swap any of the LSD carriers to any offered Gear ratio (3.7, 3.9, 4.11, 4.44)

 

But the newer viscous are "inny" type, and would require a cusrtom axle to use in an Old Gen car (EA81 or EA82)

 

input flange of the newer than 2002 models have a larger flange.....must be swapped to smaller one to use in an Old Gen.



#9 Gloyale

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Posted 07 March 2013 - 12:24 PM

Oh yeah, FWIW:

 

Welded with one axle removed til you get to the trail FTW!






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