ATF Replacement - Oil Volume

[Heineken]

Well, I feel a little unsure about asking this question here but I would like to clarify something I observed.
AT NSX are quite rare in Europe but I'm going to try my luck :-)

Currently I'm in the middle of refurbishing my driveshafts (detected the typical grease decomposition signs when changing oil this spring). It was advised to drain the ATF before removing the left drive shaft, which I did. The amount of drained oil was ~3 liters. This matches the data given in the repair manual.

As I was missing a replacement washer for the drain bolt, I bought one about two weeks later (currently a little busy). To my surprise, another 1.5 liter of oil came out of the transmission when the plug was removed. Beside the fact, that I'm now in need of buying even more ATF I would like to ask the more experienced readers whether this is normal or where the extra oil came from.

I'm aware that the transmission holds ~7 liters of oil but I assumed that it was stashed away in cavities and other dead ends inside the housing and not simply draining out given enough time ..

[britlude]

no problem asking, i suspect that why there is little AT reference data on forums!!! us AT drivers need to stick together, after all, we KNOW we are better than the MT cars :)

not that unusual to get more out, it has had a fortnight to drain down, and it only needs a little airway to be made for a section to glug!

you are right, there are many places (mainly the torque converter and valve block) for the oil to stay in the gearbox, hence why only about half comes out according to the manual etc.... but that is usually a case of unscrew the drain plug, empty it, refit plug, refill all in about 1/2 hour.... you have added an extra 2 weeks drain time, just to make sure!

[goldnsx]

Isn't the drain/fill procedure a little bit outdated? In recent years, some (mostly independant) dealers service the AT with a special filling machine which changes >90% of the oil, not only a small fraction of it. Youtube is full of videos, for example: https://www.youtube.com/watch?v=9HzL9vtv9-g Not sure if it also works on the NSX AT though.

[Pride]

Very interesting and with the music playing almost hypnotic video gold. It can be likened to almost a proper "blood" transfusion.

I've got to say that I've visited many a main dealer workshop in and around London and the south east and have never seen such a machine but if I have they probably don't look anywhere as exotic as this one. Very cool.👍

[britlude]

i've seen something like this on american sites too... i'm not sure it can be done on the NSX, as usually an oil cooler line is intercepted, and on the NSX, the oil is cooled via a oil/water heat transfer unit on the top of the gearbox, so the oil doesn't actually leave the box.... ot sure if there are any ports that can be used, but then need a route back into the box... filler tube perhaps

[goldnsx]

I've seen it the first time on youtube about 5 years ago, mostly in independant shops. Main dealers usually intend to sell new cars or new gearboxes, so they actually don't have the incentive that your AT lasts forever. They are quite common now in Germany or in Austria (first video was from there) but not at the official dealers. My independant mechanic (one man shop/w) who always has the newest machines/toys in his shop also has one.

It surely makes sense every 40k or 60k miles to do a complete 'blood transfusion' with new filters (good comparison, Clive :)), esp. as the AT in our old Audi went kaboom after 120k miles and Audi says it's a lifetime filling. Ok, yes, the new transmission DOES come with new oil, thanks Audi. Never ever...

Not sure if it works with the filler tube but a pro will know the answer.

[pralognan]

The gearbox only drains less than half. I've not found any easy way to drain the system fully, so I just drain and refill more frequently,fingers crossed!

[goldnsx]

2.9 of 7.0 l drained.
Changing it more frequently would be my way to go too.
Are there any filters within the gearbox?

[britlude]

Yup, there will be a filter in the box, but, as there's no conventional sump, getting to it would be the issue

[Heineken]

At first, thank you for the many replies!

Jonathan's explanation sounds reasonable to me as the drain is indeed at the lowest point so whatever "glunks" will end up there as well. I guess it'll be little fun adjusting for the right level when refilling .. Guess I should make an order for more ATF this evening.

Regarding the full exchange method, it's very likely not possible with the NSX (at least not the way it's done with other AT cars). They connect to the ATF pipes going from the transmission to the front cooler which contains a heat exchanger. The NSX AT does use a heat exchanger mounted to the engine and as a result the ATF is never leaving the transmission.
The only option I can think of would be to connect it to the drain and the fill-pipe (the ATL level check pipe) but unsure if that works as expected.

Hoepfully I'll find time to complete the work next week, I'll keep you updated :)

[goldnsx]

Maybe Kaz can give you some more insight as AT is a lot more common in Japan than anywhere else.

[Heineken]

That would be very helpful, indeed.
In one of his blog entries (http://www.nsxcb.co.uk/entry.php?2040-Eng-Refresh-LMA-etc-45) he reported to have drained 4 liter of ATF and another 1.1 l on top of it. As these numbers don't match with the repair manual his feedback would be highly appreciated.

[Heineken]

Completed the work on the drive shafts today. Overall 4,5 Liter new ATF as required to bring the level between the Min and Max marks.
Shifting behaviour is still quite rough (compared to state of the art automatic transmissions). I'm wondering whether that's normal or not (no second NSX to compare, unfortunately .. :)).