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?

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]

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.

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

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

just remembered this thread

Cheers

Mark

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

quote:

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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

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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

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.

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

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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Rescued attachment P1010016.JPG

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Rescued attachment P1010019.JPG

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.

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

Deffo open diff - go back to the seller and complain

Pictures for comparison: Open:
Rescued attachment non_lsd.jpg

and LSD
Rescued attachment with_lsd.jpg

sorry should have said this pic is of a viscous LSD - couldn't find a better one

Thanks, the guy has agreed to give me a refund now. Anyone selling a 3.92 lsd???

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

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

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.