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Old 02-05-2009, 11:20 PM   #1
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Default 94-95 stub axle diameter? Problems with 85 RX7 differential

What is the diameter of 94-95 Miata stub axles?

That's what I need to know!! Here's why. I am in the middle of rebuilding an RX7 LSD and ran into a problem. I pulled the LSD from an 85 RX7, which should work right? Well, I got some axle stubs that are supposedly 86-91 non-turbo RX7 stubs, but they are too large for the diff! So either these aren't the correct axles, or somehow I got an 85 RX7 LSD that uses smaller axles.

I measured the RX7 axle stubs and they are 27mm. So if Miata stub axles are 27mm as well, then I'll need to find a different diff. Which would make me sad because I'm ready to get this thing in there. Plus I just spent a bunch of money on some new parts from MazdaTrix.

Also, if Miata axles are 27mm then that means all of the FAQ and info pages on RX7 differentials are incorrect. Everything I read (and I literally read everything on this subject) says that the 85 RX7 LSD will work. I know for sure that this diff came from an 85, I pulled it myself.

Here's my problem, I'm seriously pissed off about this, I was ready to install this thing tomorrow and now I'm going to have to wait and figure this out. Damn.

Here's the 86-91 RX7 stubs that don't go into the 85 diff...
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And some other pics of the diff...

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So do I need to buy a new diff or what?

Last edited by Link; 02-05-2009 at 11:39 PM.
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Old 02-06-2009, 01:36 AM   #2
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Are you sure its from an 84-85? There are two different size axles for a first GEN RX7.

7" small axle = 25mm x 24 spline (808, RX-3, 79-83 RX-7)
7" large axle = 27mm x 26 spline

Last edited by Pseudosport; 02-06-2009 at 02:15 AM.
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Old 02-06-2009, 09:58 AM   #3
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It must be from a large axle car. There were both.
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Old 02-06-2009, 11:33 AM   #4
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Quote:
Originally Posted by Pseudosport View Post
Are you sure its from an 84-85? There are two different size axles for a first GEN RX7.

7" small axle = 25mm x 24 spline (808, RX-3, 79-83 RX-7)
7" large axle = 27mm x 26 spline
Well, I pulled it from an 85 that a local guy was parting out. I suppose it's possible that the rear end had been changed at one point or another to the small axle.

I measured the axles that came with the diff last night and they are indeed 25mm. Which means that I somehow got a small axle diff.

So the search continues! Luckily the disks and washers I bought from MazdaTrix will work in both differentials, so once I find an LSD that I can use I'll have plenty of parts to rebuild it with. It just sucks that I was planning on putting the LSD in this weekend and now I have to search for another diff. It took me three months to find this one, turns out they are extremely hard to find.
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Old 02-06-2009, 11:55 AM   #5
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Oh that sucks. As far as I knew the 84-85 rears were all the same and the small axles came in anything previous to that.

you could call 915racing.com and see if he has anything available for you.
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