Oil in the transmission

My mechanic was changing the transmission fluid and he put motor oil in the transmission instead - he said he didn’t run it very long and he drained it by taking the pan off. am i screwed?

If the engine ran at all with motor oil in the transmission pan, that motor oil was pumped throughout the transmission. Have it towed to a shop that has a tranny fluid exchange machine so all the contaminated tranny fluid can be replaced.


Yep …a pan drop only gets about 30% of the total fluid content out of the trans. Most of it resides in the torque converter. If he didn’t run it, fine. If he did, then, as stated, a full fluid exchange is required. An exchange should take about 15quarts to reduce any residuals.

he ran the engine but did not drive it - i think he is only planning to let it gravity drain over night - should i make him do more?

Yes you should. A gravity drain will not get it all out. There is a ton of fluid still in the torque converter and various other places. You need a full fluid exchange - as in all fluid. This can’t be done only through the pan.

The labor is 10 minutes. He can either unhook a cooler line at the radiator or the trans and just purge 15 quarts through the thing by running the engine. It’s EASY. VERY EASY.

Starting the engine drives the transmission’s pump. The motor oil is thoroughly mixed in the torque converter …everywhere, really.

INSIST ON IT. It’s easier than suing him later on or the hard feelings you have about it when issues show up. For the aggravation factor, it’s even sensible to pay for the fluid (HIS COST NOT MARKED UP) if he’ll do the VERY SIMPLE exchange.

thanks guys - pretty consistant response - I will make him purge the lines etc… this morning

Don’t disconnect the tranny cooler line and run the engine! You’ll pump the tranny fluid out faster than it can be added and end up with a burned out pump in the transmission.

You need a tranny fluid exchange machine to do this right.


Thanks - he told me he did a full flush so we will have to see how it goes from here

Nonsense, Tester. You pump until the flow starts decreasing and turn off the engine. A moron can do it. If you’re otherwise paranoid, you add a quart as a quart appears in the discharge.

You can most certainly keep ahead of the discharge with a funnel and bottles of ATF.

Have you installed that Titanium head liner to protect you from the likelihood of meteor showers yet?