My 2010 Saab 9-3 has an Aisin AF33 5 speed automatic transmission (same transmission as was used in a lot of Opels, Saturns, Volvos and Nissans).
The transmission has a dipstick, about 5 inches long, which is held in by a bolt. The bolt got snapped, and needs to be drilled out or extracted, so right now nothing is holding the dipstick in other than the pressure of its o-ring against the inside face of the hole into which it's inserted in the transmission.
The question is: can I drive the car a few miles on the freeway to the mechanic like this, or will fluid pressure in the transmission force the dipstick up and out and spray transmission fluid everywhere?
Every car I've owned, including my current daily-driver Saab, have transmission dipsticks that are held in just by an o-ring. Never had a problem. (There's no fluid pressure on the dipstick.)
Curious, Chuck - is your daily driver a 9-5, then?
No, it's a 9000.
Most automatic transmissions that I've ever seen with dipsticks are in the transmission's sump, which is unpressurized. The transmission's torque converter takes the rotating motion from the engine and drives a transmission pump, with the rest running to the vehicle's wheels. The transmission pump is the second component in the transmission's bell housing. The dipstick is usually located in a reserve of sorts.
unpressurized, as long as the vents are clear