Lua difficulties

Hi, I've been toying around with vehicle specific lua scripts(like the Sunburst driver assists) and I'm having a few issues. Mainly whenever I try to retrieve lastSlip and slipEnergy from the drivetrain.wheels table, it always returns 0. Another issue is when I try to update differentials engineTorqueCoef(v.data.differentials table), it works but the game doesn't actually update the differentials with the new values. Am I doing something wrong?

 

Okay so I fixed the issues of the diffs not updating by making the updateDifferentials function in drivetrain.lua a global function and then calling it. Is there a way of doing this without editing vanilla lua files though?