speeometer calibration
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1st Gear
Joined: Feb 2006
Posts: 1
Likes: 0
speeometer calibration
I just purchased a 1992 vette with a 6 sp trans. The previous owner had changed the rear axel ratio and now the speedo is way off. Any suggestion to correcting or recalibrating it. thanks 
Race Director
Joined: Jun 2001
Posts: 10,956
Likes: 681
From: Marlboro country MA
I installed an Abbott electronic ratio adaptor. See http://www.abbott-tach.com/era.htm. IT's a little black box that goes between the tranny and the computer by splicing into the speedo gear wires. Costs about $160 and can be adjusted very finely so as to make your speedometer exactly accurate.
Drifting
Joined: Oct 2004
Posts: 1,477
Likes: 80
From: Hawaii
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
As stated, you can buy a $150.00+ black box, or better yet, chances are a $10.00 - $20.00 stock gear will solve your problem. Step one, is to determine what gears are in the car. The surest way to fond out is to jack both rear wheels off of the ground and rotate BOTH rear wheels, precisely ONE full turn. The number of turns, and fractions, thereof, that the drive line turns, while the wheels make ONE turn, is your ratio. Then simply go to the CHART supplied by James93LT1 and pick the driven gear you need. Because your car is a manual, the drive gear and the VSS won't change.
RACE ON!!!
RACE ON!!!
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
Another alternative: An $80 black box
http://www.dakotadigital.com/index.c...rod/prd126.htm
It works fine for me, and can easily be re-calibrated for different tires gears etc. I used a racelogic v-box to dial it in perfectly. My first attempt at calibration was very close anyway (within 1% at 100 mph).
Note: In my case I would've had to change both gears for 3.73s (15/45 from 17/42) also my transmission output shaft splines are twisted? making yoke removal very difficult.
Edit: 14/42 would also work for 3.73s, which would require only one gear change when going from 3.07s. Anyone know if a 14 tooth gear is available? Or is this a custom gear also?
http://www.dakotadigital.com/index.c...rod/prd126.htm
It works fine for me, and can easily be re-calibrated for different tires gears etc. I used a racelogic v-box to dial it in perfectly. My first attempt at calibration was very close anyway (within 1% at 100 mph).
Note: In my case I would've had to change both gears for 3.73s (15/45 from 17/42) also my transmission output shaft splines are twisted? making yoke removal very difficult.
Edit: 14/42 would also work for 3.73s, which would require only one gear change when going from 3.07s. Anyone know if a 14 tooth gear is available? Or is this a custom gear also?
Last edited by tequilaboy; Feb 7, 2006 at 01:00 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by tequilaboy
Edit: 14/42 would also work for 3.73s, which would require only one gear change when going from 3.07s. Anyone know if a 14 tooth gear is available? Or is this a custom gear also?
RACE ON!!!
