Rear LSD - Split thread

Ben Up North

Ben Up North

can only hope to improve
Joined
Oct 1, 2017
Messages
2,115
Location
FNQ
Car Year
2004 | 1992
Car Model
SG Forester X MY05 | 92 SVX
Transmission
5MT D/R | 4EAT
Kevin said:
The SH with VDC was a great improvement over the SGs that had no traction control at all, apart from rear LSD in some.
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I thought all SGs had rear LSD.. which ones don't?
 
They might but too busy to check atm ;-)

(I've been working on forums most of the day - here and subaruforester.org)
 
Ben, all series II SGs have a rear viscous LSD. Cannot find whether the series I had or not. I seem to recall that all Foresters have a rear LSD, but cannot find the info.
 
Another offtopic is there a way to improve that rear lsd so it would like bite better. Heard somewhere aboutbghat but dont remember. Of its doable what it gives better?
 
2003 base model SG had no rear lsd . No idea which year all SG's got rear lsd's and no idea if higher spec 2003's got lsd's.
 
scalman said:
Another offtopic is there a way to improve that rear lsd so it would like bite better. Heard somewhere aboutbghat but dont remember. Of its doable what it gives better?
Click to expand...


Yes a clutch LSD rear diff is easy to do & very effective. Choices are OEM from a JDM WRX STi (mine's a V2), KAAZ or Cusco
 
Red XS said:
2003 base model SG had no rear lsd . No idea which year all SG's got rear lsd's and no idea if higher spec 2003's got lsd's
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From Subaru Forester Technical Specification P-FTB03 for the then new SG:

"All models, manual and auto, are also now fitted with a viscous limited slip rear differential"
 
So you need change all diff or just insides from jdm wrx. That would be little hard to find i guess.
 
You need to change the centre. If buying second hand you might want to do the clutch packs, bearings, etc. Keep in mind it needs to fit your axles
 
Centre of what? Rear diff? Yh i could look some wrx cars for parts so what i need to look here?
 
Centre of the diff you wish to upgrade. WRX's are no good. Older ones came with VLSD in the rear and centre and open at the front. Newer ones came with R180- well, the ADM ones did. You need to find an STI RA type diff and see if it is plated. Otherwise get a Cusco or similar.
 
Amazing info in that link.too much even. Shame. Its hard to tell about diffs from outside. Like mine says nothing on it. So if buying diff from scrapyards its so hard to tell ehat it is.
 
I wonder if you can bake a rear VLSD at high temperature to make it bind more.


Seems to work (unintentionally) for the center diff
 
duncanm said:
I wonder if you can bake a rear VLSD at high temperature to make it bind more.


Seems to work (unintentionally) for the center diff
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(ps: this is mostly tongue-in-cheek. )
 
Actually IME vLSDs work very well.

It's almost impossible to tell that they are working, unlike any of the mechanical LSDs, but just occasionally I have felt mine kick in when crossing a gravel spoon drain at the side of a dirt road. That's the only time.

If they didn't work, as some suggest, neither would the AWD in most Subarus.
 
I only appreciated my rear vLSD after experiencing my mates Outback which doesn't have a rear vLSD. My SG with rear vLSD is able to power through section with diagonal wheel spin providing it's not up too steep a hill. It doesn't feel like it's doing anything as you still get diagonal wheel spin, but the car keeps going, while the open diffed Outback just gets stuck and can't get out in either direction. My Forester can nearly always get out in one direction or another.


Is it possible to get to much temperature in the diff that it stops working? Sometimes I find if I get diagonal wheel spin stopping and then a more gentle acceleration gets me out.
 
Yes it is possible, Red, but only by doing burn outs. I've got photos of a centre diff that's been destroyed this way. F'ugly :( :( :puke:. Came out of a WRX IIRC.

The non-Newtonian fluid inside goes all black and horrible (expands) , and stops being a non-Newtonian fluid ...

I have never heard of one failing in normal use. If it does, it just turns into an open diff.
 
I just find in these sorts of situations a light throttle crawls up while too much accelerator causes excess wheel spin and you stop moving. Not sure if it's to do with rear vLSD over heating or the front right wheel scrambling away. These are the situations where the Forester can keep driving while the open diffed Outback doesn't stand a chance and needs to pick another line.
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