About half the fluid remains in the torque converter - it's normal for a drain and fill to be around 6 quarts. Make sure you follow all of the procedures bringing the transmission to temperature for the final level check while the engine is running.

 

This might be a stupid question but here it goes:

Edit: So what happens when you have a leak from the torque converter? Does that mean you cannot add CVT fluid to your CVT using the filler hole?

 

A pump cycles the fluid through the torque converter and the rest of the transmission so it's not a separate reservoir but it doesn't have a drain, so if the cvt fluid is added to the transmission it will make it's way to the torque converter. One of the reasons why the engine needs to be running to get the correct level of transmission fluid is because it's being pumped into the torque converter.

 

This makes sense, thank you so much! So if the new fluid is cycled through the torque converter and the rest of the transmission, does that mean doing repeated drain and refills will replace more of the old fluid? Because on the second drain I would expect more of the old fluid to come out mixed in with some of the new fluid.

 

Someone once posted an excellent explanation in here about the ratio of new/old fluid after every drain/fill if you attempt to get all, or most of it changed in one service. Tried, but was not ever able to find it again. Basically, 1st time if you drain 6 out of 12 and refill, you have a 50/50 mix. Try that again, and you drain half of the old fluid but you also will drain half of what you just put in. IMO, the only way you'll get most of it in one drain/fill is to pull the trans and drain the converter, unless you can rig up a running flush. Even then, I doubt you will flush out all old fluid with 12 quarts even if you can do that. Not the way fluid moves around.

 

Unless your transmission fluid was contaminated it doesn't need to be 100% replaced. The thing about motor oil is that it gets contaminated and you want to drain all of it because it's flushing contaminants of combustion. Transmission fluid degrades with heat and that's why the manual says to change it (drain and fill) every 25k miles if you do frequent heavy towing.

 

@SilverOnyx , not disagreeing that replacing all cvt fluid in an OB is not a thing, but it seems like you're saying cvt fluid doesn't get contaminated and that I'll disagree with. Gears, clutch packs, chains/pulleys all produce some degree of metal or fiber particulate just by virtue of the fact that they are in contact with each other, and boundary lubrication isn't always enough to prevent 100% of that. One difference between a modern cvt and a conventional automatic trans would be that the number of parts that work through friction are greatly diminished in the cvt, so yeah, the rate of contamination would be much less in the cvt, but there will still be some. As you rightly pointed out, towing makes fluid change a bigger concern, but I think that heat plays a bigger part in fluid degradation there.

 

Right, wear products accumulate but in light duty Subaru considers it a lifetime fluid in the USA, but in Canada there's a scheduled drain and fill every 60k which I think is a better idea.