Gearing

["Carl Buckland" <buckland@xxxxxxxxxxxx>]

In a seperate letter, I asked for dyno sheets.  That will help me maximize torque 
and horsepower with respect to gearing.  Now I want to ask about gearing from a 
track experience point of view.  Ideally, track guys should have at least two or 
three diff's, but that is not practical for most of us.  I can handle two, one a 
"stock diff," for SCCA stuff, and another gonzo diff, for tracks that need 
something different.  The stock 95 diff was a 3.15 (too high for most uses, 
although for autocross, maybe perfect, as it gives you 65mph in second gear).
The 3.23 gives you a little more jump out of the hole.  Stock on a 97 4dr auto 
was 3.38, so that is also legal for SCCA.  Then we get into the 3.46, 3.64, and 
the 3.73.   

The 3.73  goes to 55 in second (at 7000rpms), 82 in third, 110 in fourth, and 138 
in fifth.  That  sounds perfect to me, as it uses ALL the gears (except for first, 
which we only use to get off the ground anyway), and puts you in a sweet spot 
for third and fourth (and fifth).  Very few tracks have straights that exceed 138, 
especially for our horsepower challenged M3's, so 138 is fine with me.

third:  from 4000rpms to 7000rpms, it goes from 47 to 82
fourth:           "                    "                                 62 to 110
fifth:              "                    "                                 78 to 138

The problems are that the "perfect" gearing may not exactly match the max 
torque and hp bands, and what is good for Laguna Seca may not be good for 
Road Atlanta.

Any advise will be greatly appreciated.

Carl Buckland
Carl Buckland
Salt Lake City, Utah
FAX 801-531-6690 
   

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