I own a 1990 740 turbo. This evening I accidentally put a small amount of antifreeze into the transmission instead of automatic transmission fluid - a bonehead maneuver for sure. They bottles are both nearly identical blue bottles, so I thought I was pouring transmission fluid. By the time that I realized what I was doing I probably had already poured approx. 1/4 cup of antifreeze into the transmission. The car has not been driven or started since. Do I need to drain the transmission, or will a small amount of antifreeze not damage the transmission? Thank you - any advice would be greatly appreciated.

 

Im no expert but I would probably just go ahead and drain it. It is easy to drain.. then just put new fluid in.

 

Drain and flush and drain and flush. Do it maybe 3-4 times and replace the filter. I would also disconnect and purge the transmission lines. After all this is done then start it up and get it warm and then do another drain and flush and new filter again.

 

1/4 cup may not do damage... Then again, why risk it?
Do one fluid change, you'll be fine... (Anything more is excessive. And don't bother with the filter--it's just a screen...)

 

antifreeze is basically water and stuff, and likely won't mix at ALL with the oil, so it will emulsify and gum things up pretty good if left in there . I think I would want to use some kind of solvent that would flush it out. maybe, before starting the engine at all, drain the main tranny plug, add half 90% isopropanol and ATF, then drain again, refill with ATF, and then disconnect the tranny cooler line, and start the engine to flush out the torque converter, adding atf as fast as it comes out til its coming out nice and clean and clear red.

I dunno. ATF is kind of expensive nowdays, too. last time I did a regular flush of my tranny I ended up using something like 8 quarts of Castrol Transmax Multi-import.