Assuming you are using the same gears.ini file, you will need to edit the gear settings to match ratios in your gears file. Set the transmission settings in the HDV file to be a two speed, that will be the default. Add this to the upgrades file:
-----------------------------------
UpgradeType="Transmission type"
{
UpgradeLevel="2 Speed"
{
Description="2 speed transmission"
}
UpgradeLevel="3 Speed"
{
Description="3 speed transmission"
HDV=[DRIVELINE]
HDV=ForwardGears=3
HDV=Gear1Setting=0
HDV=Gear2Setting=1
HDV=Gear3Setting=2
}
}
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