Building an RX7 LSD diff

Technical info not specifically 1st gen RX7 related.
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ian65
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Re: Building an RX7 LSD diff

Post by ian65 » Tue Jan 13, 2015 3:11 pm

Lucky wrote:MR TOOL, can you offer any advice as to which flavour of MX-5 diff will fit in this process? I might be able to get hold of a Torsen diff from a top-spec Series 2 MX-5, will that be OK? I'm guessing a Torsen diff is preferable to a multi-plate one
viewtopic.php?f=11&t=170

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1986 Series 3 13B Turbo II
http://rx7fb.com/viewtopic.php?f=2&t=2400
1992 Peugeot 205 1.9 GTI
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Lucky
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Re: Building an RX7 LSD diff

Post by Lucky » Tue Jan 13, 2015 3:39 pm

Ta. Damn, how many threads did LSDs run to? :?

TOOL
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Re: Building an RX7 LSD diff

Post by TOOL » Tue Jan 13, 2015 7:17 pm

As that other thread says, you need a 7 inch diff head (that's measured by the crown wheel size).

Afaik, all the 1.8 MX5 diffs are 7 inch. The trick is working out which ones have the Torsen diff though, not the open diff. I prefer Torsen type 2 over type 1, they just look more robust. I prefer clutch type LSD over Torsen, as you can rebuild them and "tweak" them.

Note, some MX5 are 3.9, 4.1 and 4.3, but I've never been able to find a 4.3, and no-one seems to know how to work out which cars had them (if any in the UK market)

Here's a useful link for IDing Torsen centres: http://www.miata.net/garage/diffguide/
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re japi
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Re: Building an RX7 LSD diff

Post by re japi » Wed Jan 14, 2015 5:29 am

Here is one link which has good info
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ian65
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Re: Building an RX7 LSD diff

Post by ian65 » Wed Jan 14, 2015 8:40 am

re japi wrote:Here is one link which has good info
some great info there, where did that come from?
1986 Series 3 13B Turbo II
http://rx7fb.com/viewtopic.php?f=2&t=2400
1992 Peugeot 205 1.9 GTI
1975 Honda SL125 Street Scrambler

TOOL
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Re: Building an RX7 LSD diff

Post by TOOL » Wed Jan 14, 2015 8:49 am

That's from the Mazdaspeed Competition Parts Catalogue.

It's right near the bottom of the RX7 manuals on www.foxed.ca
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Lucky
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Re: Building an RX7 LSD diff

Post by Lucky » Wed Jan 14, 2015 10:27 am

Great stuff, thanks guys. I'll try to snare one then

re japi
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Re: Building an RX7 LSD diff

Post by re japi » Wed Jan 14, 2015 11:45 am

Friend of mine found it. :)

Lucky, I have diff for sale. Just started a topic in sales section. Also, its for sale in Facebook rx7fb site...

biznatch
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Re: Building an RX7 LSD diff

Post by biznatch » Wed Jan 14, 2015 12:46 pm

The competition part manual mentions the torsen type 2 being a higher ratio than the type 1 - anyone on here know which torsen is closest to our stock ratio?

TOOL
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Re: Building an RX7 LSD diff

Post by TOOL » Wed Jan 14, 2015 2:15 pm

They were talking about the bias ratio, not the gear ratio.

Note GSL-SE is 4.11 gears and UK S3 is 3.9.

When fitting one of these diffs, you need to remove the Torsen cerntre and fit it in the RX7 carrier, with the RX7 ring and pinion, otherwise you'll get binding on the RX7 suspension components (watts link).

See page 1 of this thread.
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