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Author: Subject: Sierra LSD Types
rayroni

posted on 13/1/03 at 10:33 AM Reply With Quote
Sierra LSD Types

What Limited Slip Diff's are available from the Sierra. I'm aware that 'the 4x4' has a LSD, but which model has one - the XR4, 'standard 4x4' or Cosworth?

If I assume right that all those models are fitted with one, what are the differences between them (ratio's and casing/mounting)? and how do I stop someone selling me a none LSD - do they look any different from the outside.

Thanks for any info received.

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zetec

posted on 13/1/03 at 07:18 PM Reply With Quote
There appears to be two size of LSD fitted to the Sierra. It's the size of the top front mountings which you should check, there is 7 inch and 7.5 inch. I think the larger one was fitted to the Cossie spec cars, and also has a larger input flange. Easy way to check if LSD is by turning the input flange and the output flanges should both turn together in the same direction, if they turn in opposite then not LSD. The LSD I got looks just the same as the non LSD one. Suspect 7inch is most common, if self build you can choose which size to use but most spec 7inch. I think ratios differ between cars as also fitted to Granada. Think they range from 3.9 to 3.3/1.
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Stu16v

posted on 13/1/03 at 08:05 PM Reply With Quote
*Alarm bells ringing*
To check if you have an LSD, you gently turn a drive shaft flange. If the other one turns the same way, you have an LSD. If it goes in the opposite direction it isnt (but you probably worked that out already...) Turning the input flange (prop flange) should make them both turn the same way for either diff. If it doesnt, leave it where it is, because if its fitted to your car, you will go round in circles....





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geoff shep

posted on 13/1/03 at 09:11 PM Reply With Quote
They don't have to both go the same way with non-LSD - one can be stationary and the other will go twice as fast. That's the point - unlimited slip. But yes, one shouldn't go backwards.
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Alan B

posted on 13/1/03 at 09:39 PM Reply With Quote
Geoff, true one can be stationary, if held or stuck, but if is free it will turn the opposite way if non-LSD.
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Stu16v

posted on 13/1/03 at 10:57 PM Reply With Quote
quote:

They don't have to both go the same way with non-LSD - one can be stationary and the other will go twice as fast. That's the point - unlimited slip. But yes, one shouldn't go backwards



You are right Geoff, but the point being you wont get the driveshaft flanges turning in opposite directions by turning the prop flange.

quote:

Geoff, true one can be stationary, if held or stuck, but if is free it will turn the opposite way if non-LSD.



Just for clarity, thats if you turn a driveshaft flange Alan...





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Alan B

posted on 14/1/03 at 12:03 AM Reply With Quote
Yep, that's what I tried to say.....I think...(very badly)

One wheel can be held still while the prop shaft turns the other wheel only.....with non-LSD.

And, with the prop held still the wheels will turn turn opposite to each other with a non-LSD when you turn one by hand.

Damn....that sounds even more confusing...sod it...

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Liam

posted on 14/1/03 at 10:22 AM Reply With Quote
Hello...

XR4i's didn't have an LSD as standard. All 4x4's do and they're all 3.62:1 as standard, granny 4x4s too. All 4x4s, even cossie, are 7". 7.5" LSD's are found on 2WD cossie and 24V scorpio as standard - probably be some on 12V V6 grannies/scorps too.

7" are most common and fine for the average Locost. 7.5" are popular with Dax Rush owners and their big V8s.

Liam






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Liam

posted on 14/1/03 at 11:15 AM Reply With Quote
Oh whoops - forgot 2 litre 4x4s, which have 3.92:1 diffs.






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geoff shep

posted on 14/1/03 at 07:31 PM Reply With Quote
Well boys, I think we managed to simplify that one for him !!??


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rayroni

posted on 15/1/03 at 01:24 PM Reply With Quote
Thanks to one and all for that. Now know where I can source one from. And I think I know how to tell none LSD's and LSD's. To sum up (and hopefully not cloud the issue further).....

If an LSD is sat in front of me, and I hold one drive shaft output, by turning the prop-shaft flange, I will feel resistence in the 'propshaft rotation' and the held driveshaft flange will try to turn.

If it is a None-LSD and I perform the same test, then as I turn the propshaft, there will be no drive felt in the held drive shaft, no resistence (apart drag of gearoil) and the unheld driveshaft will turn freely.

Is that a valid test, without having to remember, which wheels go in which direction, depending on which shaft is turned........ ??

Cheers!!

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kingr

posted on 15/1/03 at 04:34 PM Reply With Quote
That sounds about right, but it's probably easier to just turn one of the output shafts and see if the other goes in the same direction or opposite direction. An even better way would be to find out exactly how these things work, and then not only would you know how to tell what type it is, but also how they do what they do.

One question of my own, but related, I know there are two different types of drive shafts/connections for LSD, and I seem to remember they may be directly related to whether it's got disc or drums, so, can I have a breakdown of possible car/diff/driveshaft type/brakes please? I'm sure others would find this helpful too.

One last questions, less related, but interesting none the less. How would you tell if it had an atb? And does anyone care to explain to me how they work.

Kingr

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gjn200

posted on 15/1/03 at 06:03 PM Reply With Quote
Rightyoh, For 7" sierra all lsd diffs have lobro shafts, as do non lsd with disks. Drums use tripod shafts. For the avon its designed for drums and non lsd, but "according to chester sportscars" that I spoke to last week, if you want an lsd and disks you have too turn down the abs bit to fit through the hub carrier and switch sides with the callipers, ie trailing will become leading.





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