2003 SG XS Forester No vLSD?

BeeJ

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Joined
Nov 12, 2012
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106
Location
Perth Western Australia
hey guys,

Been doing a lot of reading regarding the SG vLSD and based on what I have read apparently a 2004 SG XS Dual Range 5sp Manual forester should have vlsd right?

Well i have my car on axle stands the other day and did the old rotate one wheel to see if the other turns the same direction test.

Guess what, it spun the opposite direction. To me that means I have an open diff...

really!!

do any SGs have open diffs standard?
or could my vLSD be knackered?

If its knackered, can you service it or getting working again?


I know many people say vLSD is useless but I feel robbed that my SG doesnt have it!
 
It maybe depends on the markets while here, all SG have an LSD...
 
My SG has (or had) LSD; not sure if it's still working. It needs a reasonable amount of wheel slip to engage, so doing it by hand probably won't engage it.
 
Gidday BJ Kevin & all

Kevin said:
My SG has (or had) LSD; not sure if it's still working.
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Unless the vLSD has been physically damaged in some strange way, I can't see how it can work as a diff at all without the vLSD working?

It needs a reasonable amount of wheel slip to engage, so doing it by hand probably won't engage it.
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The fluid in the diff is a Prince Rupert fluid (? Non-Newtonian fluid I can't find any references to Prince Rupert, other than his drops), like tomato sauce - the higher the torsional stress placed on it, the hotter it gets, the stiffer it becomes. In a diff, this causes the two shafts to tend to rotate together, same as the vLSD in the centre of the gearbox.

As it is designed to have the weight of a car on it and fairly high rev difference between the wheels applied to it in order to work, it is highly unlikely that you will see any effect at all turning the wheels by hand ... It is quite unlike a mechanical diff in that way (and lots of others ... ).
 
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Ok thanks guys
If anyone has their SG on a jack or stands can you do the spin test?
Interesting to see if its the same on all vLSDs
 
G'day again BJ

BeeJ said:
Ok thanks guys
If anyone has their SG on a jack or stands can you do the spin test?
Interesting to see if its the same on all vLSDs
Click to expand...

I would NOT recommend doing this sort of thing.

On chassis stands/hoist, all that will happen is that the wheel you grab will stop (open diff); or the wheel you grab doesn't stop, and you may well lose a substantial part of your anatomy ...

This sounds a tad dangerous IMNSHO ...

vLSDs can only really be tested under the conditions that they are designed to work under - i.e. on the road/track, with the weight of the vehicle on them. Either there, or on a properly equipped test bench ...

If I am wrong about any of the above, someone please correct me.
 
I was talking about turning one wheel by hand and looking at the other. I'm not suggesting anyone run their car on stands or hoist
 
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Just found some articles on this subject that may clarify the workings for me, and anyone else who is hazy about the details ...

Here, Viscous Couplings (not that kind ... :lildevil: ):
https://en.wikipedia.org/wiki/Viscous_coupling_unit

And as used in diffs:
https://en.wikipedia.org/wiki/Limited_slip_differential

And particularly the bit about the vLSD (seems that Kevin is right, the vLSD can deteriorate with time, and I presume the use to which it is put. Good on yer, Kev :cool:), here:
https://en.wikipedia.org/wiki/Limited_slip_differential#Viscous

However, this doesn't seem to be the case with Subaru vLSDs, as if it were, surely the centre diff would show the same deterioration? It patently doesn't.

Anyway, all interesting reading.

[EDIT] A further description with graphics for the various kinds of diffs here:
https://auto.howstuffworks.com/differential5.htm
[end edit]
 
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Why not just remove the fill plug and have a look? One of the reasons I'm getting the KAAZ diff is because my car has an open rear diff
 
BeeJ said:
Well i have my car on axle stands the other day and did the old rotate one wheel to see if the other turns the same direction test.

Guess what, it spun the opposite direction. To me that means I have an open diff...
Click to expand...

This is perfectly normal for the rear diff even if it's a VLSD.

Remember the VLSD is still essentially the same design as an open diff (so yes, the wheels will spin in opposite directions in your type of test) and simply has the addition of the viscous coupling unit between the two outputs.

As mentioned by others above, there will need to be a fair bit of difference in the speed (or direction too in this case!) of rotation for the coupling to act and provide resistance and you may not achieve this just spinning the wheels by hand.
 
BeeJ said:
Ok thanks guys
If anyone has their SG on a jack or stands can you do the spin test?
Interesting to see if its the same on all vLSDs
Click to expand...

I have an SG diff in my SF.

I did that test one day when it was on a hoist at the tyre shop. Both rear wheels turned the same way. At that time I had an open diff in the front. Performed same test on front and wheels turned in opposite directions.
 
Ratbag said:
However, this doesn't seem to be the case with Subaru vLSDs, as if it were, surely the centre diff would show the same deterioration? It patently doesn't.
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yes it does.

My centre diff was stuffed: I had it replaced with a tested viscours coupling. It now puts power down through all four wheels whereas previously it was much more prone to slippage.

If I were wrong in this regard, places like all drive subaru and other gearbox builders would not make any money out of selling tested visous couplings. Clearly they do make money.
 
I read alot on subaruforester.org of people having failed centre vlsds. I believe bluefox who is also on here has a failing centre vlsd at the moment.
 
Gidday Greg

Dulagarl said:
yes it does.

My centre diff was stuffed: I had it replaced with a tested viscours coupling. It now puts power down through all four wheels whereas previously it was much more prone to slippage.

If I were wrong in this regard, places like all drive subaru and other gearbox builders would not make any money out of selling tested visous couplings. Clearly they do make money.
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The one in Roo1 certainly still worked perfectly after 234,000 kms; but that doesn't mean that all do.

Perhaps your car is not an ideal example, being as highly modified as it is?

I am equally certain that you are right. Any mechanical device can and will fail eventually.
The closest to "everlasting" was John Harrison's clock. The running train and all other parts were made entirely out of wood. He didn't trust metal parts ...
It was stopped for the first time for repair and service work some 200 years after it was first put into service.
 
How's this. My grandfather bought an axe in the late 1800's. Just before he died, he had to replace the handle, and a few years after I was born, dad replaced the head. Other than that, the axe has always worked perfectly and nothing else has needed attention. I guess living in the centre of town meant it did not get a lot of use. Especially since I bought a chainsaw.
 
Gidday Rally

LOL!

I've got a trailer just like my Grandfather's axe ... :iconwink:
 
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