Building an RX7 LSD diff

Technical info not specifically 1st gen RX7 related.

Re: Building an RX7 LSD diff

Postby RamoNZ » Tue Mar 10, 2015 12:52 am

Good work. Tooth pitch/width are also likely to change so a matched pair may still be the only solution?

Refer your pics of the S2 vs S3 CW/P set - although these are actually the same ratio, the tooth count changes.
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Re: Building an RX7 LSD diff

Postby A7RXY » Tue Mar 10, 2015 7:53 pm

Tool I have deleted the whole post for you.

Dibs
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Re: Building an RX7 LSD diff

Postby TOOL » Tue Mar 10, 2015 7:57 pm

spirit r wroteColonYou have to change speedometer drive or wheel dimension sometimes.
Thomas


SPEEDOMETER GEARS:

The speedometer gears and gear housings between all the late model(1984+) 'M' transmissions interchange. If you have installed different rear ratio gears or different diameter tires then you will need to change the speedometer gears in the transmission to keep the speedometer accurate. The speedometer gear housing bolts to the transmission and is easily removed since it is external to the gearbox

Mazda makes speedometer gears for the late model 'M' gearbox with 17-23 teeth. The steeper the rear ratio gears or the shorter the tire diameter the more number of teeth is needed to compensate. The 90-91 Miata comes from the factory with a 20 tooth speedometer gear (which makes the 4.30:1 gear about 5mph fast). The pitch of all the speedometer gears is the same and only the diameter of the gear is different (1978-mid83, with the exception of the 626, use a coarse drive gear and are not interchangeable). The different gears housings are offset to account for the diameter change (see picture)

Image

FYI, If you cannot find a 626 or late model Miata unit then you can make one by using the abundant 1979-83 RX-7 17 tooth coarse gear drive, which is the same diameter as the 22 and 23 tooth fine tooth drives. This makes the housings interchangeable and then only the drive gear itself (22 tooth = part number 8854-17-441A) needs to be purchased.

Asked and answered th:
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Re: Building an RX7 LSD diff

Postby TOOL » Tue Mar 10, 2015 8:02 pm

FYI, this is a table of the known gear sets available highlighted in yellow afaik:

Image
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Re: Building an RX7 LSD diff

Postby TOOL » Tue Mar 10, 2015 8:05 pm

A7RXY wroteColonTool I have deleted the whole post for you.

Dibs


That's not quite what I was after mate, but hey ho.

Ramon, I've got matched pairs. S2 and S3 will never be interchangeable, but I wonder if a 43 tooth crown wheel can be matched with different pinions to alter the ratio.
This is the condensed version.
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Re: Building an RX7 LSD diff

Postby TOOL » Sun Mar 15, 2015 6:47 pm

TOOL wroteColonIf anyone else is interested in a lower ratio ring and pinion for their diff, let me know and I will keep searching. It's been a lot of research and some trial and error, but I'm starting to get results.

Let me know what ratios you want.


Sunday night bump on this.
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Re: Building an RX7 LSD diff

Postby BezRx7 » Mon Mar 16, 2015 5:51 am

Hi guys

Can I swap in the gsl-se 26 spline lsd and axles into my 82 GSL housing?

My plan theoretically is to swap out all the gsl parts from the differential. Use the GSL-SE third member, the Miata Torsen 2 lsd and moser 26 spline axles

Thoughts??
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Re: Building an RX7 LSD diff

Postby kenwhiteside » Mon Aug 22, 2016 11:10 pm

Reading the below

http://www.mx5oc.co.uk/forum/yaf_postst ... atios.aspx

Anyone got a 3.636 ratio rear end in an fb? Would certainly make 1st more useable and 5th better on the motorway.
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Re: Building an RX7 LSD diff

Postby TOOL » Tue Aug 23, 2016 5:45 am

No one has that drive ratio. It would be awful.

If you want a taller 5th gear fit an FC box. You'll have better 1-4th as well.
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Re: Building an RX7 LSD diff

Postby Rubarotary » Sun Nov 06, 2016 7:04 pm

Hi tool,

I've got 2 diffs laying here but the crown Wheel is 8inch And 43 And 41 teeth, axles Have to be 30 splines.
Any idea from what Car they are ? Housings look alot like the one from a fb .
The're Both (atleast i think ) lsd type
Is it possible that there from a T2 or 929

Any Help is greatly appreciated.

Image
Image

Image
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