[ainarssems]

I used to think that there is thermostat in the box but was not sure and looking at previous posts it seems like there is no thermostat in the box.

In regards to thermal expansion different fluids will behave differently in different temperature ranges.

I vaguely remember reading it somewhere that for the 5HP24 box with about 12l of ATF the volume from cold 20C to working temp of 100-130C will change by 0.7-1l.

I also know that different engine oils expand differently, some oils hardly expand at all and others quite a lot. So with one oil I could check level after car has been standing overnight and compare it to running up to temp, then waiting 10 minutes for oil to drain and it would be pretty much the same level. But with different oil it could be barely minimum level cold and over max level when hot.