You are correct. The transmission has to be fully warmed, engine running and car in park when checking on the warm line. Make sure the transmission itself is completely warmed before you add fluid to make sure you don't overfill.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record