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Re: Miata 1.6l VLSD Rebuild

To: Chris Herring <yoonchris@batnet.com>
Subject: Re: Miata 1.6l VLSD Rebuild
From: Keith Hearn <khearn@Legato.COM>
Date: Thu, 27 Jan 2000 14:10:20 -0800
In message <l03130303b4b667e20507@[209.24.152.87]>, Chris Herring writes:
> Hi all  << except Scot...cover your ears, Scot! :) >>
> 
> I recently purchased a factory VLSD for my CS Miata. There is a local shop
> who can rebuild the diff using different discs, which will cause the diff
> to lock up a little sooner/more. The parts are Mazda factory parts, and
> apparently the diff will still be within factory spec. But neither me nor
> the shop has any documentation to back up the claim that the diff is within
> spec. So two questions:
> 
> 1. Any thoughts about whether the rebuild is SCCA-legal?

>From http://www.moutons.org/sccasolo/car_class_stock_rules.html#s13:

  Parts available as replacements through the dealers parts department,
  the factory, or any other source which do not meet standard part 
  specifications (e.g., hardness, size, etc.) are not legal in Stock 
  Category, except as specifically provided elsewhere in these rules. 

So even if the new discs are from the factory, if they're not the same as
  came on the car, they're not legal for stock, unless we can find
  somewhere ele in the rules that say they're ok.
 
Hmm, doesn't look good. Section 13.10.K says:

  Limited-slip differential, transmission and differential ratios,
  clutch mechanisms, and carburetion, fuel injection or supercharger 
  induction systems must be standard as herein defined. 

Here's the definition of standard part (section 12.4):

  12.4 Standard Part

  An item of standard or optional equipment that could have been 
  ordered with the car, installed on the factory production line, 
  and delivered through a dealer in the United States.  
  Dealer-installed options or deletions, except as required by 
  factory directives, no matter how common or what their origin, are 
  not included in this definition. This definition does not allow 
  the updating or backdating of parts. 

So my reading of the rules is that different discs than were originally
  installed at the factory wouldn't qualify as stock.

Sorry, but that's what it looks like to me. And I'm not even biased,
  since we're no longer in the same class.

> 2. Any thoughts about whether it's worth a couple of hundred dollars to do
> this?

I doubt it. If it puts you out of your preferred class, certainly not. :)

Even with a little better lockup, it's still a VLSD. If you're going to
  bump yourself out of CS, you might as well go with a Torsen LSD.

  Keith Hearn
  '99 Miata 10AE "Sexy Sadie" the Sapphire Shark
  Milpitas, CA




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