Why Measure Trans. Fluid with Engine Running?

[jhellwig]

It is all how the transmission is engineered that determines how it is checked.

There are some engines that can be checked while running. Usually large stationary ones.

 

[Lubener]

Originally Posted By: slacktide_bitog
Transmission dipsticks are never accurate anyway, except Honda.


Only way to determine that is filling a dry transmission to specs, following the procedure and then checking.

 

[wymi516]

Is it better to do a drain on hot trans oil?

 

[Oro_O]

Originally Posted By: wymi516
Is it better to do a drain on hot trans oil?


It does not matter much. ATF is thinner than most motor oil (it is equivalent to a 20w at temp., ~7cSt at 100C), and flows well at normal ambient temp. Also, on most designed pans, the welded-in threads for the drain bolt create a lip that traps the last 1/8" or so of pan depth in, so it will never come out w/o a pan drop. Which is a good thing on a high mileage unit before swapping fluid. This way the new fluid does not pre-load with contaminants by solubilizing the residue in the pan bottom.