To clarify, Joel; the fluid should be checked hot, in park, with engine idling. The purpose of having the engine idling is to be sure that all the work passages and servos are full.
After doing work on the trans we have to engage all the gears to fill all the elements first. If you are testing a hot trans, it is assumed that the thing has been through all the gear positions.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician