andrew-theasby
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| posted on 31/10/06 at 08:51 PM |
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Viscous LSD??
Hi, ive just bought a (supposedly) limited slip diff, its a 7" 3.92 sierra jobbie, and has bolt on shafts, so could well be the 2.0 xr4x4 diff
its supposed to be, but i thought to test if it was a limited slip you held the input flange, turned a wheel flange, and the other wheel turned the
same way?? Well this one doesnt, so is that not the case with a viscous type, rather than a plated one, or is there a way of telling if i take the
back plate off? Ps it doesnt have the tag on it anymore. Hope someone can advise please?
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ReMan
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| posted on 31/10/06 at 09:27 PM |
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Doesn't sound like an LDS at all unfortunatly 
Mine def rotated both outputs the same way, also 3.92 is a non-lsd ratio. 3.62 is lsd
I stand corrected, 2.0 twin cam is 3.92
[Edited on 31/10/06 by ReMan]
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Johnmor
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| posted on 31/10/06 at 09:51 PM |
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3.92 lSD
I think there is a 3.92 LSD from, as you say, from a 2.0l sierra 4x4.
I have 3.62 LSD and tested as below.
To check, hold one out put flange and turn the input shaft. if LSD this should very difficult to do and any difference is vey small.
If so, good choice, as i feel mine is too high geared.
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mookaloid
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| posted on 31/10/06 at 10:28 PM |
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Johnmor is the nearest:
If you hold the input still and turn one of the out puts then LSD or not the other output will always turn the opposite way. This is the way diffs
work.
If when doing the above the output shaft is hard to turn it is a LSD if it is easy it's open.
You can confirm this by taking the back off and looking at the bit that the crown wheel is bolted to. The LSD has a large lump which contains the
viscous coupling whereas in the open diff the crown wheel is bolted to a relatively thin steel web thing.
If you take the back off and post a pic I can confirm this for you.
Cheers
Mark
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andrew-theasby
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| posted on 31/10/06 at 10:37 PM |
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Thanks for the tips everyone, ive tried all of the tests, and it doesnt really seem too difficult to turn either way, but its lost a fair bit of fluid
in transit, so that might explain that. Ill definitely post the pics as soon as i can, might not be till tommorow tho. Thanks again. Ps, 3.92 is
available as a lsd, there just really rare, so ill be gutted if this isnt as ill have paid way over the odds for an open diff 
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mookaloid
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| posted on 31/10/06 at 10:49 PM |
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just remembered this thread
Cheers
Mark
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hillbillyracer
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| posted on 31/10/06 at 11:08 PM |
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If it's easy to turn it doesnt mean it aint an LSD, just that it aint a good one
Take the plate off the back, if you can see gears on the inner ends of the output stubs then it's an open diff. If it's just a big round
piece of machined steel with a crownwheel then it's an LSD of somekind
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mookaloid
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| posted on 31/10/06 at 11:35 PM |
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quote:
Originally posted by hillbillyracer
if you can see gears on the inner ends of the output stubs then it's an open diff. If it's just a big round piece of machined steel with
a crownwheel then it's an LSD of somekind
Usually true but not with the sierra LSD you can see the gears on both kinds
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oddsaabs
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| posted on 1/11/06 at 02:09 AM |
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Buyer beware when it comes to buying Sierra LSD diffs. I recently acquired one, paid to have it shipped, and upon inspection found it not only to be
an open diff but quite worn as well. Still trying to get my money back and not holding my breath.
I would recommend always getting a code number from the case and comparing it to the excellent data listed elsewhere on this site. I have learned a
lesson the hard way and now compare all code numbers to the printed data I keep at hand or personally inspect it before money changes hands.
Best of luck to you.
J
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NS Dev
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| posted on 1/11/06 at 09:27 AM |
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all the diffs fitted to XR4x4's, 2.0 or v6, are LSD's, so if it is from one it is either knackered, or you have been told porkies.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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mcerd1
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| posted on 1/11/06 at 09:43 AM |
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If your getting no resitance form the diff it might just be that its a totaly knacked LSD
this thread on the FSOC tells you how to translate the
tag on the back - but even if you can read it - the tag might have been changed
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andrew-theasby
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| posted on 2/11/06 at 08:57 PM |
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Hi, sorry ive taken so long getting the photos, here they are. glad i did take it apart now though, cause i found 3 bits of a smashed circlip in
there and this is supposed to be a fully reconditioned diff!!
 
Rescued attachment P1010015.JPG
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andrew-theasby
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| posted on 2/11/06 at 09:03 PM |
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.
 
Rescued attachment P1010016.JPG
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andrew-theasby
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| posted on 2/11/06 at 09:09 PM |
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.
 
Rescued attachment P1010019.JPG
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DIY Si
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| posted on 2/11/06 at 09:18 PM |
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Have to say it certainly looks like an open diff to me. If possible give it back to who ever you brought it off, get your money back and then
contemplate slapping them. 
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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Minicooper
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| posted on 2/11/06 at 10:08 PM |
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Open diff it is, the viscous part of the diff should be to the left of the crownwheel, the planetary gears, etc are similiar in either type of diff
David
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mookaloid
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| posted on 3/11/06 at 12:43 AM |
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Deffo open diff - go back to the seller and complain
Pictures for comparison: Open:
 
Rescued attachment non_lsd.jpg
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mookaloid
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| posted on 3/11/06 at 12:43 AM |
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and LSD
 
Rescued attachment with_lsd.jpg
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mcerd1
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| posted on 3/11/06 at 08:23 AM |
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sorry should have said this pic is of a viscous LSD - couldn't find a better one
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andrew-theasby
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| posted on 3/11/06 at 10:20 PM |
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Thanks, the guy has agreed to give me a refund now. Anyone selling a 3.92 lsd???
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chriscook
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| posted on 4/11/06 at 10:40 AM |
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3.92 LSDs are pretty rare as you probably know. It may be worth getting a refund -£30 the 3.92 open diff is worth keeping it and looking for a much
more common 3.62LSD and chaning the LS bit over to the 3.92 diff.
Just a thought....
Chris
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andrew-theasby
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| posted on 4/11/06 at 05:37 PM |
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A very good thought, i too had thought about that, but i arent over confident about how well its been rebuilt, with that circlip falling out. Anyone
know where i could get another one from, and where can i find out how to re-assemble it, i assume theres a bit of torque loading to do?? Is there any
other bits i need to buy like crush washers etc? The circlip thats missing is the opposite one to that in the photo.
 
Rescued attachment P10100231.jpg
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Rob Allison
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| posted on 13/11/06 at 01:11 AM |
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If your wanting to have a 3.92 the just fit the viscous diff into the 3.92 case. Must say though the sierra lsd's aint that good as they allow
to much power to go to the traction less wheel.
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