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Changing differential gear ratio
http://forums.ctzcc.com/viewtopic.php?f=4&t=6964
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Author:  jtang [ Thu Mar 21, 2013 11:48 am ]
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I took a video of the behavior when I was first trying to diagnose the problem...

http://www.youtube.com/watch?v=7AxgtB1coXg

Not sure how it happened, but the 29 spline axles go in, but they don't properly "lock in". I think the O.D. of the 29 spline axles are just slightly smaller than the 30 spline stubs so it can slide in and even turn with the front flange if everything is out of the car. Once you put a little pressure on it, though (i.e. bolt everything up), you can see and hear that the axles aren't connecting to the diff properly.

Author:  Frank T [ Thu Mar 21, 2013 3:12 pm ]
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Ahhhh.......now I wonder if the 29 spline and 30 spline axles are maybe different diameters? That would allow the smaller axle to pop in there and snug up, but there wouldn't be enough contact to allow it to turn under force. That's just what I'm envisioning in there ~ I might not be correct.

What it sounds like it might be doing tho, is shaving tiny metal slivers off the smaller splines, which would contaminate your differential. I wouldn't turn it anymore if I were you. You already know it doesn't work ~ no good can come from turning it any more, and if it's shaving metal off the smaller axles when you turn it, you might sprinkle fragments throughout the gear system.

Author:  jtang [ Thu Mar 21, 2013 7:19 pm ]
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Spot on Frank. That's also why I have reinstalled the old differential for the time being. :)

Author:  Paul [ Fri Mar 22, 2013 9:32 am ]
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The Z31 axles are longer and can bind. The 280zx will work. If this helps.

Author:  jtang [ Sun May 05, 2013 8:48 pm ]
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Finally, finally, FINALLY got this thing done.

Got a set of z32 NA axles and another set of z31 NA axles.... slapped them together to build my hybrid axles.

Image

z32 NA axles (top two), z31 NA axles (bottom two), and 30 spline axle stub that fits into my LSD.

The idea is the stub that fits into the LSD terminates in a 5-bolt flange. The z31 axles don't have this flange end (both turbo and non-turbo). The z32 axles do terminate in this 5-bolt flange on the diff-side.

So.... disassemble the z32 axle...
Image

and steal the 5-bolt flange parts
Image

Take apart the z31 NA axle on the diff side... cut it shorter and weld on the inner race from the z32 axle:
Image

And assemble!
Image

And install!
Image

Been breaking in the LSD. Everything seems to be working well! Will have to do more testing.

I'd love to take credit for this awesome stuff but people in the z31 community have worked this all out in the past. It is also known to work and on z31 cars with much more HP and torque than my little nonturbo, so I'm not worried about breaking things. It is "method #4" outlined here:
http://www.xenonz31.com/vlsdInstall.html

Author:  Frank T [ Sun May 05, 2013 11:44 pm ]
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"Necessity os the mother of invention" :D :thumbs_up:

Author:  Paul [ Mon May 06, 2013 8:22 am ]
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Yea, I forgot you are working on a Z31, not a 240. So, anyways, Job well done, looks good. :thumbs_up:

Author:  Gregmatic [ Mon May 06, 2013 9:34 am ]
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nicely executed Justin, you get these projects done like a machine!

Author:  jtang [ Mon May 06, 2013 10:56 am ]
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Gregmatic wrote:
nicely executed Justin, you get these projects done like a machine!


Wouldn't have been possible without your help! :thumbs_up:

Author:  jtang [ Tue May 07, 2013 11:48 pm ]
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Okay so I broke the welds! Not sure if the design isn't strong enough period or if certain types of welding makes it possible and others not.

Open diff going back in... halfway done. Will continue in the wee hours of the morning before work...

Back to the drawing board!

Author:  Frank T [ Wed May 08, 2013 7:57 am ]
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:cry:

Author:  Paul [ Wed May 08, 2013 11:38 am ]
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I know this feeling. :mrgreen: :cry:

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