How do you adjust VSS

[trippyjoey]

It's an 0D mask and under the RPM/VSS Ratio constant it's currently set at 40.718. I got bigger tires on it and might be re gearing so would like to learn how to adjust it. In the parameter comments section it shows a formula but if I try using it with the factory tire size I don't get 40.718 I get 18.926.

[billygraves]

It's an 0D mask and under the RPM/VSS Ratio constant it's currently set at 40.718. I got bigger tires on it and might be re gearing so would like to learn how to adjust it. In the parameter comments section it shows a formula but if I try using it with the factory tire size I don't get 40.718 I get 18.926.

What you are viewing is the N over V ratio, as we termed it inside GM Calibration. This is only for TRANSMISSION MPH speed calculations which is used in all MPH tables. I would just leave this calibration alone. (It determines the MPH that is used in TCC On/Off speed and the Shift light on Manual trans IF equipped.)

I was wrong about the speedo being changed by the DRAC module in your 88-91 ECM truck. It is changed via a pin set up on the back of the Inst panel. See the below to read about how. Sorry that I was wrong. Just an old fart I guess. (DRAC was 91 forward with electronic auto trans.)

[ony]

here is a good write up if I can get it to post http://www.chevytalk.org/fusionbb/showtopic.php?tid/258562/