I have had two different opinions on how to check the transmission fluid in my 2005 Auto tranny.
One says leave it running in PARK and remove the fill plug. If fluid runs out it is OK. The other says leave it running in DRIVE ( obviously jacked up) and check the fluid level. Which one is correct?
Also, any tips/ watchouts when changing the transmission filter?

 

Park is correct. Back in the '60s, we use to check in drive. But after a few too many people got run over by the car because the park brake did not hold, GM revised the procedure to check the AT in "Park".

As per the SM:

Start the engine and allow the engine to idle until the transmission fluid temperature has reached the value specified.
Depress the brake pedal and move the shift lever through the gear ranges, pausing a few seconds in each range. Return the shift lever to the PARK range.
Raise the vehicle on a hoist. The vehicle must be level with the engine running and the shift lever in the PARK range. Refer to Lifting and Jacking the Vehicle in General Information.
Caution: The engine must be running when the transmission fluid fill plug is removed, or excessive fluid loss will occur. Transmission fluid may be hot. Since the actual fluid level is unknown, stand clear when removing the fill plug. Have a container ready to capture any lost fluid. Do not turn the engine off with the fill plug removed, as you can be injured by hot transmission fluid being expelled out of the oil fill opening.

Remove the transmission plug.
Important: The transmission fluid may darken with normal use and does not always indicate contamination or oxidation.

 

Great, Thanks for the info.

 

Whatever happened to the dipstick?? Seems we're regressing. Am I missing something?

 

The oil level indicator and adaptor tube were eliminated years ago for a cost savings.

The idea is that the trans is filled at the plant and unless there is a leak, the trans fluid will never get low. No more vaccumm valve modulators to fail and suck trans fluid into the intake.