spitfires
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Re: Diffy, ratios

To: Ryan Smith <shmitty99@hotmail.com>
Subject: Re: Diffy, ratios
From: Andrew Mace <amace@unix2.nysed.gov>
Date: Sat, 11 Jul 1998 22:25:21 -0400 (EDT)
On Sat, 11 Jul 1998, Ryan Smith wrote:

> Today I drove across the state to check out the 72 Spit I've been asking 
> questions for.  Its a sure thing that the car is mine.  This thing is 
> spotless and mostly original....

> Should I opt for a 3.63, a 3.89 or another 4.11 like it 
> has now?  The car is a stock 1300 with no modifications and no o/d 
> (yet).  Also could someone tell me what rear ends US mk's 1-3 have.

Ryan, I'd stick with the 4.11:1 with an "original" '72. The engine can 
use the lower gearing. An alternative, though, might be the 3.89, in 
which case it would be good if he could throw in a speedo from a '71 to 
maintain "accuracy" (such as that might be).

All pre-Mk.IV Spitfires had a 4.11:1 diff as stock, but it's a different 
unit -- not as "beefy" as the later unit. To use one of those, you'd need 
to change u-joint flanges on your '72's axles and driveshaft, and you'd 
need to plug the two center spring hold-down stud holes after mounting up 
the swing-spring you have. Of course, it might not be that easy to find a 
4.11:1 in the later, beefier diff style, as they were only used on the 
'72 in the U.S.

--Andy

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