'02 Corvette gear swap question

[Patches]

I just swapped the stock 2.73 diff gear for a 3.42 and a Yank 3200 TC in my '02 coupe A4 Corvette. I downloaded the original tune to save it as the original and then upgrade a copy with the new gear ratio. When I check in the Speedo Calibration section, it shows the ratio as already being 3.42 instead of the factory 2.73 that was originally in it. :nixweiss:

Is there somewhere else I should be changing the rear gear ratio to adjust the shift points, etc?

TIA

[Blacky]

I just swapped the stock 2.73 diff gear for a 3.42 and a Yank 3200 TC in my '02 coupe A4 Corvette. I downloaded the original tune to save it as the original and then upgrade a copy with the new gear ratio. When I check in the Speedo Calibration section, it shows the ratio as already being 3.42 instead of the factory 2.73 that was originally in it. :nixweiss:

Is there somewhere else I should be changing the rear gear ratio to adjust the shift points, etc?

TIA
Just repeating this reply here for the benefit of others...

The H0103 (diff ratio) is not used by the PCM to calculate the speedo needle position or shift speeds. It is really not used for anything other than calculating rear axle torque loads for torque managament.
However, EFILive uses it to figure out some of the speedo settings so it is good to have it set to what is in the car, but if it is set wrong then it will not affect much in the way the vehicle operates. Most factory calibrations have it set wrong anyway.

The shift points are controlled by the H0104 setting. That settings contains the number of trans output shaft revolutions per mile and the PCM calculates the shift speeds from that value and H0101.

H0101 changes the overall speedo settings and it will affect the speedo needle and shift points.
H0104 changes the shift points but not the speedo needle.
So get the speedo needle reading correctly by changing H0101, then get the shift points shifting at the calibrated speeds by changing H0104.

H0102 will be a calculated value on the corvette because the speedo pickup is on the rear axle (after the diff). Normally (on a non-corvette) H0102 is either 17 (manual trans) or 40 (automatic trans). However, because it is after the diff on a corvette, it is 40/H0103. i.e. if you had 3.42's then H0102 should be 40/3.42=11.6959.

P.S. That info above is for a C5. The C6 is different - it uses tire diamater for speedo calculations.

Regards
Paul

[Patches]

Thanks Paul.