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I have always checked my transmission's oil level hot and with the engine running just like the dipstick told me to. But I just discovered I can check it cold and with the engine shut off after it sits overnight and it's every bit as accurate. I just marked my dipstick at the "cold" level which is about 4-5 inches above the hot and running level.
When you shut your engine off your torque converter immediately begins to drain until the oil level reaches the bottom of the drive snout. And as it drains the level in the pan rises until the oil rises up into the dipstick tube.
To me it makes more sense to check it cold as that's when I check my other fluid levels.
I think the reason why they recommend checking it hot and with the engine running is most people only raise their hoods when they gas up and by that time the oil has warmed considerably and a good portion of the oil is still in the torque converter.
When you shut your engine off your torque converter immediately begins to drain until the oil level reaches the bottom of the drive snout. And as it drains the level in the pan rises until the oil rises up into the dipstick tube.
To me it makes more sense to check it cold as that's when I check my other fluid levels.
I think the reason why they recommend checking it hot and with the engine running is most people only raise their hoods when they gas up and by that time the oil has warmed considerably and a good portion of the oil is still in the torque converter.