Power-glide ATF fluid level - Strange reading

[rustbelt]

Checked the ATF fluid level on my 1965 Monza 110. Not having any problems with the trans, it shifts fine. Had driven the car awhile to warm up the PG, parked in the driveway (level), put in Neutral, applied the parking brake and left the car running. Nothing showed on the dipstick.
I proceeded to add fluid, continuing to check the stick. After aprox. 2 quarts, suddenly the fluid went from zero showing to being half way up the dipstick. After siphoning the fluid back out via the tube, started the car, checked, and again the dipstick showed no fluid.
I turned the car OFF, checked the fluid level again and it registered FULL.

Did this a couple of times, each time having the same result. Car running - no fluid level, car off - full fluid level.

The dipstick is correct length. Any ideas why when checking while running as per the manual, nothing is showing on the dipstick yet fluid level shows full when checked not running?

Thanks for any help given.

[joelsplace]

It should show way over full when the engine isn't running.
If nothing shows on the stick add 1/2 quart and check again.
Once you show something on the stick just add a little at a time to sneak up on it.
You can also get false readings from oil running down the inside of the tube.
Look at both sides of the stick to see if the level is the same on both sides to verify you aren't getting a false reading.

[rustbelt]

Thanks joelsplace for the response. I'll recheck today and see what I come up with.