GM actually uses the secondary shift schedule for 4LOW, so the pins that get triggered for 4 low are the ones that trigger teh secondary shift schedule in a MD application. In the ALLISON DOC software in a MD OS, they can simply go in and select secondary shift schedule and activate it and input the shift schedule into the table. The GM OS's are locked down pretty tight after the ALLISON sale from GM back in 06, so those cal's are locked down according to there sales agreement with GM when they sold the ALLISON brand off.