flak monkey
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| posted on 22/1/06 at 09:02 AM |
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7" or 7.5"
I am right in thinking that all sierra diffs with push in shafts/drum brakes are 7" arent I?
Theres been a bit of confusion as to whats 7" and what 7.5" and it just confused me further... lets see if I got i right: 7.5" diffs
were fitted to granadas and scorpios, and some, but not all, cosworth sierras. Everything else is 7"?
David
Sera
http://www.motosera.com
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zzr1100rick
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| posted on 22/1/06 at 09:21 AM |
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wrong i took a diff out of a sierra twincam with rear discs and it was 7.5 ( bugger ) so got another with drums 7 
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zzr1100rick
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| posted on 22/1/06 at 09:22 AM |
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ment to say drum one was 7.5
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flak monkey
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| posted on 22/1/06 at 09:44 AM |
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Dammit... so even some of the diffs with push in shafts, and drums were 7.5"?
Whats the likely hood that one from a 1990 GLSi fitted with drums is a 7" diff?
Whats the measuerment across the mounting flange for a 7" and 7.5"?
Cheers,
David
Sera
http://www.motosera.com
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RichieC
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| posted on 22/1/06 at 10:00 AM |
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According to the list from Ford, the 2.0 GLSI has a 7" diff. However, some 2.0 twin cams had the rare 3.91:1 diff in 7.5" guise.
Rgds
Rich
[Edited on 22/1/06 by RichieC]
 
Rescued attachment diffratios.jpg
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piddy
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| posted on 22/1/06 at 10:52 AM |
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I believe that the estates were also fitted with 7.5".
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RichieC
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| posted on 22/1/06 at 11:50 AM |
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Ive not heard that before. The 2.3 diesel estate has a 7" diff.
Its quite possible that over the years, the diff has been replaced on the car and could bear no resemblance to what the VIN plate says or what it
should have fitted.
There are always exceptions to the rule, but the list above is a very good rule of thumb.
Rgds
Rich
[Edited on 22/1/06 by RichieC]
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MikeRJ
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| posted on 22/1/06 at 03:51 PM |
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So is the only problem with the 7.5" diff the extra weight? Or is there something else that limits it suitability?
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RichieC
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| posted on 22/1/06 at 04:49 PM |
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Depends on what its going into. Theres no benefit to ba had with 7.5 over 7 unless thats what comes along at the right price.
There are issues with them being a tight squeeze but removal of the back plate seems to solve that one.
I almost ended up with a 7.5 but just because thats what there was at the time. Im glad I held out for the 7", but I wanted an LSD anyway.
Rgds
Rich
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flak monkey
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| posted on 22/1/06 at 05:23 PM |
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Wasnt there something about the 7.5" diff being wider across where the mounting bolts go through? Or was that just my imagination?
Cheers,
David
Sera
http://www.motosera.com
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Liam
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| posted on 22/1/06 at 05:46 PM |
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Very rare to find a 7.5 diff on a sierra (unless it's a 2WD cossy of course). According to Rich's list the only sierra with a 7.5 diff is a
2.8 EFI(?) from Sweden - not too many of them over here I imagine. That list is very old, though, so it's possible they got rid of a few 7.5
diffs on later twin cams. Still quite rare though.
You can easily tell them apart if you hunker down at the back of the car and have a look. The 7" diff has a nearly semi-circular rounded bottom,
wheras the 7.5" is a whole lot bigger and has a much flatter squarer bottom.
Liam
 
Rescued attachment 7vs7.5diffs.jpg
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Liam
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| posted on 22/1/06 at 05:49 PM |
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And you're right about the different top mount widths. Conveniently/coincidentally the 7" diff measures 7" accross the top mount, and
the 7.5" diff measures 7.5". Many available chassis are designed to take a 7.5" diff which means a 7" diff has to be shimmed an
extra 1/2" to fit.
Heres another shot of them for comparison...
Liam
[Edited on 22/1/06 by Liam]
 
Rescued attachment 7vs7.5diffs2.jpg
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flak monkey
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| posted on 22/1/06 at 07:23 PM |
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Thanks Liam...
Looks like this one that I have been keeping an eye on is a 7.5" one then! (I know it says it in the description, but wasnt sure that layout
existed) Even though it has push in shafts and has drum brakes..! Must be a rarity!
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=4605313249
David
Sera
http://www.motosera.com
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RichieC
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| posted on 22/1/06 at 07:26 PM |
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Yeh thats a 7.5, easiest way I find is to look at it from the front, the 7.5 you cannot see the bolt hole all the way through and the strake which
runs vertically up towards that isnt all the way on the 7.5
Rgds
Rich
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flak monkey
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| posted on 22/1/06 at 07:28 PM |
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Damn...its NBG to me then! Anyone else want this rather rare layout?!
David
Sera
http://www.motosera.com
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MikeRJ
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| posted on 29/1/06 at 03:26 PM |
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Well, that's made me happy! I bought a diff from a friend for £40 who assured me it came from his own early 2WD Cosworth (I bought it as I was
after an LSD, not knowing about the different diff sizes at the time).
Since finding out about the larger diff, I'd assumed it was a 7.5" diff, but according to the pics and advice above it's definately
a 7". Now I just need a set of normal Lobro style driveshafts, which should be far easier to find than Cosworth ones.
Should I avoid ABS driveshafts for any reason?
[Edited on 29/1/06 by MikeRJ]
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