the_fbi
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| posted on 26/7/05 at 10:40 AM |
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Is a 7.5" "Cosworth" LSD diff suitable for a blade BEC install?
All the various diffs are a bit of a mystery to me, i know there are 7" and 7.5" versions (apart from the physical difference in size
I'm not sure what the other differences are).
I'm wondering if a 7.5" Cosworth 2WD LSD diff is suitable for a Fireblade engined MK Indy I'm planning to build?
Apparently the flanges may be different to a 7" diff but these can be changed to fit the "normal" sierra driveshafts?
Any ideas what the ratio would be, any good/bad things I need to be aware of with this unit?
I've also heard of Freelander diffs being used, which are sub £200 new and of a suitable ratio for a bec, is this a worthwhile upgrade from a
sierra diff?
Thoughts/feedback appreciated.
Thanks
Regards
Chris
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phelpsa
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| posted on 26/7/05 at 10:48 AM |
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7.5 will be a bit heavy.
Adam
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mookaloid
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| posted on 26/7/05 at 10:48 AM |
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The 71/2" is physically quite a lot bigger and presumably heavier which is not ideal.
Don't know much about the Freelander diff but it looks quite a neat thing.
Cheers
Mark
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Mr G
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| posted on 26/7/05 at 10:52 AM |
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I write an essay and then it does'nt post it (and i'm logged in)
Ratio of that diff should be 3.62
Roughly you want a 3.38/3.18 for a BEC build.
One for sale HERE
You can take the lsd unit out of a diff and put it in one without (i.e lsd a 3.18 or 3.38)
Here's (as a rough guide) where they lived:
 
Ford Diff Ratios
[Edited on 26/7/05 by Mr G]
Normal is getting dressed in clothes that you buy for work and driving through traffic in a
car that you are still paying for - in order to get to the job you need to pay for the clothes
and the car, and the house you leave vacant all day so you can afford to live in it.
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the_fbi
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| posted on 26/7/05 at 11:01 AM |
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Thanks guys, great info/feedback.
I presume you can't take the LSD from a 7.5" and stick it into a 7" can you?
ie. if this 7.5" LSD goes cheap, do I buy it just to stick its LSD into a 7" non-LSD unit?
ta
Chris
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mookaloid
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| posted on 26/7/05 at 12:29 PM |
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I've never tried it.....
but I can't imagine why ford would make a 7 1/2" case for a diff when it would fit in a 7" case.
Of course I could be wrong...
Cheers
Mark
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Mr G
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| posted on 26/7/05 at 12:45 PM |
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Just a bit more on the driveshafts :
Sierra 4x4 inc sapphire cosworth have 100mm flanges and a 7" lsd diff
Sierra Cosworth RWD have 108mm flanges and a 7.5" lsd diff
Granada cosworth's are supposed to have a 7.5" diff with lsd and 100mm flanges. The scorpios had lsd as an option as they had traction
control.
You can remove the rear back plate of the diff and then get to the circlip (one each side) that retains the flange. Once you remove the circlip the
flange can be slid out as its on splines. I'm not sure of the number of splines on 7.5" diff flanges compared to 7" flanges.
I also would of thought that one lsd unit fits all too.
Sorry its slightly vague but every little helps
Cheers
G
[Edited on 26/7/05 by Mr G]
Normal is getting dressed in clothes that you buy for work and driving through traffic in a
car that you are still paying for - in order to get to the job you need to pay for the clothes
and the car, and the house you leave vacant all day so you can afford to live in it.
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Jon Bradbury
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| posted on 26/7/05 at 12:47 PM |
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Lot of discussion on this topic on the Sierra forum.
Basically you can grind off the excess casing to get a 7.5" diff fit a 7" mount, but it is risky as you can go through the casing really
easy. The other thing you need to do is tap a new thread in the bit you just ground off.
Not recommended.
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chrisf
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| posted on 26/7/05 at 01:08 PM |
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If you're not feeling so adventurous, I'm interested in talking to you about taking the diff innards off your hands. U2U if you're
interested in selling.
--Chris
[Edited on 26/7/05 by chrisf]
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the_fbi
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| posted on 26/7/05 at 03:02 PM |
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Thanks for the info G and the pointer Jon.
Sounds like its perhaps not the best thing to do!
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