Well I changed the ATF in the CVT yesterday. According to the service manual, it's supposed to take 4.2 litres when it's changed (if the vehicle has the tranny cooler, which mine does). Anyhow, before removing the drain bolt, I removed the fill bolt (to make sure it would come out and I would be able to refill). When the fill bolt came out, tranny fluid shot out (almost over to the passenger tire, completely missing the drain pain, doh) and a fair amount of fluid drained out of the fill hole.

Per the service manual, the fluid level is supposed to be between 0 and 0.5 mm of the bottom of the fill hole. Would it be safe to assume the tranny was slightly overfilled based on what came out of the fill hole?

After draining the tranny, I measured the amount that came out and filled 4 one litre bottles.

When I refilled the tranny, it only took about 3 and 3/4 litres before it was at the bottom of the fill hole. Drove the car with no problems and no change in the level.

Thinking the fluid might expand when hot, I left the car overnight and checked the level cold this morning and it was still just at the bottom of the fill hole.

My next thought was that maybe the tranny cooler was empty and that would take the extra 1/4 litre. Thinking the tranny cooler might have some sort of thermostatic control, I drove the car for quite a while (highway and city) and checked the level when I got home. It was still at the bottom of the fill hole.

Anyway, everything is working fine, I just have an extra 1/4 litre of fluid laying around.

Has anyone else changed the fluid in the CVT and had something like this happen?

Um, I would be afraid that now the car is undriveable. It sounds like the plug you removed is not the fill plug. I would get confirmation of that from a dealer before I drove the car with only that much fluid in the CVT. Burning that baby up woudl be very expensive.

Umm, no. I might have been born at night, but it wasn't last night.

I have the service manual, and have worked on enough vehicles in my lifetime to know what transmission fluid looks and smells like. The vehicle HAS been driven since I changed the fluid, with no ill effects. Also, 1/4 of a litre is 250ml. The manual states 4200ml (4.2 litres) for a drain and fill. 250ml short in a 4200ml fill in not a lot of fluid given the overall capacity of the tranny.

My thinking is that the tranny was overfilled in the first place, as I've never had tranny fluid exit a fill hole before and per the service manual, the level should be at the bottom of the fill hole (where it currently sits after I've changed the fluid) and not over the fill hole.

How it would even get over the fill hole is beyond me unless it was filled from the drain hole with a pressurized line (like at the fast lube places where they don't add oil from a bottle, but just dial up the required quantity and it's pumped through a hose directly into the engine - shuts off automatically when the quantity dialled up has passed through). Maybe the last time this was changed (I'm the second owner I don't know) some technician just dialled 4.2 litres into the machine and pumped it into the tranny via the drain hole (hey less work only removing one plug right?) and then screwed the drain plug in while ATF was spilling out.

Anyway, I'm quite comfortable that my tranny is filled to the bottom of the fill hole as PER the service manual.

If my CVT self destructs, I'll gladly repost here and admit the error of my ways to save someone else the pain.

How did the fluid look when you drained it? I know this "CVT" transmission is a new technology, not sure if there's a lot more friction going on in there. Coming from an Rx300 (which is plagued with bad tranny design) i can't help but wonder if i should take preventative measures on the rx400h transmission?

I also changed the rear diff fluid (and when I removed that fill plug, the fluid level was exactly where the service manual indicates - 0 - 0.5mm below the bottom of the fill hole - it just dribbled out slightly when I removed the fill plug) and that fluid came out looking almost like new. Still bright red and not smelling much different than fresh out of the bottle. Mind you, the rear diff doesn't see a whole lot of action on the AWD system in this Lexus, unlike my previous Subaru Outback which was true AWD (front and rear diffs always powered).

The CVT fluid was darker than fluid fresh out of the bottle, but not dark enough to warrant any concern. It also smelled pretty much like new fluid. If you've ever drained a tranny of fluid that was in longer than it should have been, you'll know the smell and colour that would cause concern - very brown fluid and an almost rotten smell. I didn't have any of that with the rear diff or the CVT.

Keep in mind that I'm the second owner of the vehicle. I don't know what maintenance the previous owner had done. The maintenance guide does recommend tranny and diff fluid change at 96000km here in Canada. I bought the vehicle at 115000km, so it may have just been done. Just as an aside, the guide also recommends the Super Long Life Coolant is good till 160000 KM, but should be changed at 128000 KM ONLY in Canada.

FYI, both the CVT and rear diff use Toyota ATF WS (ATF World Standard) which is Toyota's most recent forumula. I don't know if it's synthetic or not (96000km change interval would lead me to believe it might be or maybe a synthetic blend). I know it's only considered a so-so fluid at some oil specific and Toyota specific sites (www.bobistheoilguy.com and www.totyotanation.com), but to do both the rear diff and CVT you need about 6 litres and it's about $9 a litre here in Canada (probably cheaper in the US). To me that's not a lot of money to ensure longevity of the diff and tranny. I plan to change the fluids every 48000km just for my peace of mind (and I like tinkering).

Isn't the fluid good for 90-100K miles? People have that many miles on 'em already?

90,000 miles is specified in our owner's manual, but apparently, the Canada RX400h requirements are different. Regardless, some owners will change the fluid earlier.
I'll probably have the coolant changed after 5 years, rather than the mileage listed in the manual.

Yup. The Canadian guide recommends 96000 KILOMETRES for CVT and rear diff. The coolant is also recommended to be changed at 128000 KM, but elsewhere it's 160000 KM

Based on my experience with my GX470 and the ATF-WS fluid it expands when heated. So there is a chance you may have changed it when the vechicle was warm or hot. The GX470 requires you to use a scantool to read the transmission fluid temperature to get a accurate reading on the fluid level. You need to becareful that you dont have to do something similar before checking the fluid level on your RX400h. There is a alternative way to read the ATF temperature so you can set the correct level. Do you have the service manual for the RX400h in a hard copy or PDF? I would like to get the instructions to change my dads ATF on his RX400h. Can you help?