colenzae

salimshah

The wording keeps changing. Please understand what the manufacturer states and then it is up to you to follow or make your informed choice.

Since there are no bye products generated due to use, within normal operation conditions the manufacturer states the factory filled fluid should last the life of the hybrid transaxle. They have determined this by experimentation. What is the life time of transaxle? That is not published. I would estimate that to be 100K miles (your number can vary). In hybrid the fluid is not used for clutch action so it does not heat up as much.

Users on the other hand determine good/bad by color change and have opted to replace the fluid more frequently. Dealers on the other hand down play the need and go by the manufacturers recommendation.

Follow what you want to do .. and go for even replacement of fluid every 1k mile. But somewhere you will make a determination of milage you want to change the fluid and the manufacturer has determined it to be lifetime. Just dont mess up in the process and avoid over-fill or under-fill.

For hybrids .. you also drain practically all of the fluid, while in non-hybrid a good portion remains in the system.

Salim

colenzae

I could not make an informed choice because the manufacturer lied to me. By doing so, they essentially made my choice for me. If the manufacturer of the vehicle states that the unit is sealed and fluid change is not possible, what is the consumer to do other than leave the transmission alone. If they had said, "the fluid is designed to last the life of the transmission and change is not neccessary, BUT, we can change it for you if you feel more comfortable changing it," that would have been entirely different. But they flat out lied to me and I feel that is absolutely unacceptable. As do many other members of these forums.....

salimshah

So what is the interval for fluid change that you follow? It is your vehicle, you can choose to do what you think is right.

Salim

colenzae

That is an interesting question. This question of the hybrid transaxle fluid change started when I bought a Lexus HS250H with 70,000 miles on it. Me being very **** about fluid changes wanted to change them all so I know where I am starting from. A used car, you never know how often they were changed. So when Lexus told me it could not be changed, I drove the car another 100,000 miles before someone in these forums sent me a PDF of the location of the fill and drain plugs on this cars transmission. I then immediately changed the fluid.
I also own a 2002 RX300 AWD. I am the original owner. I change the trans fluid in this car roughly once every 20-30,000 miles. I only do a drain & refill OR flush the trans with fresh fluid as described in these forums. Every 100,000 miles, I drop the pan and change the filter. I have 270,000 miles on this car with no transmission issues.
The Hybrid is an interesting question. Since there are no clutches and fewer moving parts than a conventional transmission, I believe I would be comfortable changing the fluid once every 30-50,000 miles. This brings up another question. Toyota has told me that the rear differential on the AWD Highlander Hybrid uses conventional gear oil. Others in these forums and on YouTube use Toyota WS fluid, just as the main transmission. What is the correct fluid??? Is Toyota miss informing me yet again??
How about other hybrid owners out there? How often are you changing your Hybrids trans/rear fluid and what fluids are you using?

tempestv8

The FWD inspection mode details can be found here: https://www.clublexus.com/forums/hyb...ance-mode.html

It is basically to keep the engine running to warm up the fluid, and not cutting out simply because it's trying to save fuel, which is what hybrids do.

As alluded above, a drive around the block would probably achieve the same desired effect of warming up the fluid.

Back to the original query, the circled plugs are indeed the drain/fill plugs. For those DIY enthusiasts embarking on this task, my experience is that the drain plug generally needs a sharp, firm whack with a metal mallet, just to "wake it up". Otherwise it may not come off. The fill plug generally comes off without too much effort.

MellonC00

I change the fluid on the front transaxel every 30K miles and that of the rear every 60k miles. My car is AWD.

ukrkoz

On a hybrid vehicle, rear drive is electric only and, in nutshell, is miny copy of the front PSD - Power Split Device.
Rear uses exactly same fluid as the front - World ATF. Or, any good ATF for that matter.
Rear one is 2.4 qrt, front is roughly 4.2 qrt, both are fill to overflow via fill plug.
Starting 2012, front end fill plug was moved to the tire well side of the front PSD, so no, they are not on the same side. You need short end L shaped 10mm hex wrench to undo it, as it's very tight space to get to. Easiest is to remove driver side wheel, you can see plug right there.
There are MANY fill plug look a likes on the engine side of PSD. So it depends on the year, your vehicle was manufactured. Upper pluf on 2012 looks identical to older fill plugs but, has metal shield behind it, when removed. What does not even allow to insert any filling hose into it.
DO NOT undo drain plug UNLESS you opened fill plug. They are greatly torqued and, normally, a cheat pipe is involved.
Now, to change, not to change, how often.

PSD ATF is said to be lifetime. I know many hybrid drivers that never replaced it and had no issues. Me being me, I replace it every 50 k miles, just because. There is no rule to it. If you want to waste time and money and do it more often - fine.

Reason being, ATF in PSD does zero hydraulic work. None. It is splash lubricant for moving epicyclical gears inside. That's it. As the result, it does not really overheat or is being used somehow else. MGs are cooled by inverter coolant. hence, there may be point to it not really going bad - as it simply is not loaded with much work.

paperthin

No kidding. I had better take a closer look at mine.

Nick682

This Lexus dealer is misinforming you. I have had the same issue with Lexus, so anytime I have a serious question like this I call several dealerships service departments and ask the same question then cross-reference the answers I get. I've learned that half of the service writers don't have a clue. If the service writers don't have the answer I ask them if they can go back and ask a tech to make sure. I live in Southern California and I consulted with Lexus of Thousand Oaks and Lexus Santa Barbara. I checked with Lexus Thousand Oaks twice and both times the service advisor walked into the back and spoke with the techs. I got new information each time that was useful, but both times they told me that they recommend doing a 100k service interval. They say technically if the fluid is good at 100k you don't need to replace it and that is why the manual says to check the fluid (apparently they have a machine that analyzes the fluid composition). When I called Lexus Santa Barbara the service advisor didn't have a good answer on the interval and when I told her what Lexus Thousand Oaks said she changed her tune and agreed with me. Lifetime fluid or not, it won't last forever and 100k is a pretty long interval but you could be on the safe side and do 50k. The reason for all of this ambiguity, in my opinion, is that Lexus designed it with these models to discourage anyone from doing their own service. The gearbox is sealed with no dipstick, they use a machine to determine if the fluid is bad and they don't have a replacement interval published only an inspection interval which for most people is really hard to do since it doesn't have a dipstick. Further making it complicated is the fact that it's long life fluid and it doesn't need replacement as often as normal fluid. All of this designed to get you into the dealer to use their expensive machine to check the fluid. I don't think it will hurt anything to do 100k intervals but I'd say 50k is better. Just a warning that when I did mine the gearbox made a knocking sound the first time afterward. I put in the same amount I took out so I don't understand exactly why this happened. I then pumped more fluid into the gearbox till the fill hole was streaming out fluid, replaced the plug and the noise went away. So definitely get under the car while the engine is running and listen for any "underfill" noises if you do it on your own.

Nick682

I have a 2008 RX 400h and spoke with the most experienced Lexus tech my dealer has today. He said the hybrid transmission on my vehicle has two big motors bathed in the transmission oil. It doesn't use the oil to shift through gears like a normal transmission, it's just to lube and cool the motors and the drive shaft they are connected to. So, yeah, you're right that they are not super sensitive to a slight overfill. With underfill not so sure though because the motors and driveshaft may not get proper lube. He said the way he does them is that he fills the transmission case until it streams out of the fill hole and that's it--just like you said. Puts the fill plug back in just like a differential as a mild stream is running down. The fill hole on my vehicle is even with the drive shaft which makes sense because you want oil at the level of the driveshaft. I do think it's a good idea to run it through the gears on a very short drive around the block and then recheck and pump a little more fluid in till overflowing once again.

The first time I did mine I followed the specs and only put 4.1qts and drove around and had a mild knocking sound from the gearbox right after that I had never heard before. That's when I did the second fill and noise totally went away. When I filled the second time no fluid came out when I pulled the fill plug so I know it was a little low compared to the factory fill. I have an oil cooler on my transmission for the towing package so perhaps it went there?? Some people if they underfill may not notice the noise and I'm sure it's not good if it makes noise for a long time, so after this experience, I do recommend the second check after running the vehicle around the block.

One interesting story the tech told me is that on some models there is another fill plug on the very top of the gearbox. He didn't know for sure what the top plug was for but he speculated it may be a way to run a fill hose through the top of the gearbox with the side fill plug off and that way it would be easier to see the fluid stream out of the side fill hole that is level with the axle since you don't have a hose in the fill hole while filling it. Funny thing though is that he knew a guy who filled it from the top hole without removing the side fill plug and he filled up the entire gearbox with fluid. He said the car still ran fine and there was no damage to the transmission but that it triggered a hybrid overheat warning light code after being on the freeway. I'm not sure but I speculate that if the fluid heats up enough it will expand to trigger a pressure sensor or something like that, or maybe the airspace that normally exists there helps dissipate heat more and once the gearbox is totally filled it actually builds up heat faster. I made a YouTube video explaining how I changed my fluid and what the tech told me (it will be redundant to most people on this thread, but maybe help newcomers):

Rosscoe83

I have been following this thread since I bought my LCPO '15 RX450h last year. When I took it in for it's 65K maintenance (oil change and tire rotation) they called and said that the tech recommended that I change the trans fluid. Not really necessary but highly recommended. The cost was about $230 so I said go for it. I could have done it myself but I qualify to join AARP and the money won't break the bank. I was actually glad that they recommended it and didn't give me the line about it being a sealed system/lifetime blah blah blah.

paperthin

Finally did it. I have had the fluid for a long time, too long. @250k kms front was chocolate, no pink, rear was still pink tinge but dark also. Fit 4L in front and 2L in rear exactly, both filled to overflow state. I used hand pump in rear and funnel for front. Nobody talks about the crush washer, i didn't realize it was there, but I am comfy reusing an AL crush washer more than once. Happy I did the ordeal, very inexpensive, I know I should have done it sooner. The front is exactly like the youtube video, and on my 2010 the fill and drain plugs are opposite sides. I put my pinky in the fill hole on the front to ensure it was atf, sure enough nice dark chocolate was in that location. All closed up and no leaks. Did this in my garage with vehicle on jack stands for the front.

After driving, no noticeable difference.

tempestv8

Except for that good feeling on the inside, knowing that the transmission is not swimming in a dark, worn out fluid that is effectively way past its useful service life.
Good job, well done!

I have a theory on why the front diff fluid is always darker than the rear - its because the fluid is subjected to far higher temperatures due to the large electric motor. Ergo the front transmission has its own cooling system to control the high temperatures. But the fluid still darkens. The rear electric motor is significantly smaller in size and also doesn't work anywhere near as hard or as often as the front, so perhaps that's why it doesn't have it's own cooling system. And since the fluid doesn't get anywhere near as hot due to lower duty cycle and smaller motor, the fluid doesn't darken anywhere near as the front gearbox fluid.

salimshah

My thinking was the heating happens due to conduction (metal casing) from the engine block.

Salim