Out of my maintenance manual for my IS350.....

Transfer Case/Transmission:

The transfer case/transmission
and transmission fluid are a completely
sealed unit. Therefore, periodic
checks and replacement of the transmission
fluid are not required, and
there is no dipstick on the transmission.
Any repairs that require adding
or replacing fluid should be performed
by a qualified technician following
procedures in Lexus service
and repair publications.

So pretty much they are saying you do not have to change the transmission fluid...ever? But you can if you want? I will definitely want to change the transmission fluid. At what mileage would it be appropriate? Southeast Texas where temperature is well over 90F 75% of the year.

ALL transmissions require service. Heat is the enemy of lubricating oils. The rule of thumb in the past has always been about 15k miles. BMW does the same thing. I had an older 5 series, in which the tranny had never been serviced. At about 125k miles, the trans started to go. When I found a reputable transmission shop, (interestingly enough, a former BMW certified mechanic), to rebuild it, (to the tune of $3200), he told me that the car manufacturer knows that the trans will last, in most cases, at least 100k, and by that time, the car will be out of warranty, and as a result, they are no longer responsible to make the repairs, but they certainly reap the rewards of those who come in to have the trans rebuilt. My suggestion, if you are planning to keep the vehicle for an extended period of time, is that you find a good reputable independent mechanic, and have the tranny serviced on a regular schedule.

I honestly would think so. When I am due for my 15k mile service I will ask if they can flush and replace the transmission fluid also.

The transmission went out on my IS350 at 38,000 miles. Wouldn't go past 35mph. Had some internal error code pop up. Unfortunately, the IS350 transmission is not servicable, meaning they can't open it up and repair it. They ended up replacing it with a new unit. Well they say new but it's really a remanufactured unit.

So they can open it and service it then.

Sounds like somebody did.

Yeah really if it can be remanufactured then someone had to have opened the thing up to fix what was wrong. So can I get a consensus on a proper interval for replacing fluid? 15k?, 30k? or when?

If i wanted to change fluid I'd wait at least to 35000 miles.

"They" is the operative word above. I'm sure JustFlyin meant the transmission wasn't "dealer serviceable", not that the original manufacturer, sub manufacturer, or specialty house couldn't open it and service it. I bet Lexus has a cost/benefit analysis for all parts to determine whether it should be repaired or replaced when it is on their dime.

CrunchySkippy, you are correct. The dealer will not repair, only replace. Mitsubishi is the same way with their new CVT transmissions. If something goes wrong, they'll just pop in a new one.


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Wait, hold up here.

"They" in this case is Lexus. Correct? Lexus doesn't service thier transmissions, but will warrentee someone elses work on rebuilding a transmission they make. So my point is the transmissions are servicable, just not by the dealer. They have a swap service. The trans they take out goes to the place that does the rebuild, and you get someone else's rebuilt tranny in it's place. It's actaully a smart program.

^^^yup!

Agreed. I think we are saying the same thing.

I think so to. To my knowledge, no dealer selling any make does transmission work.

So you think the dealership will change the fluid for me? Or give me a big lecture about how "it doesn't need to be changed" and "we can't do it."

I haven't really been able to make up my mind about this yet to be honest. BMW, Mercedes Benz, Jaguar, Lexus and a few others all have the sealed transmissions now. It's really hard to argue with that many engineers. They all seem to agree this is the way to go, and more and more are going this way. I mean, as hard as it is to beleive, I also would have never thought that car makers would be able to reliably engineer a naturally asperated stock 300+ hp V6. I remember when we were chasing the 1 hp per cubic inch dream. So anything is very possible when they say it's better to just leave the transmission alone. Let's not forget that the cooling system went thru this same morph years back. There was a time when you should have changed the antifreeze yearly. Now it's almost maintenance free as well. I do know one thing though, have you looked into how much the transmission fluid costs per quart yet? LOL!! That might change your mind about doing a tranny flush. LOL!!

Yeah you are probably right. I asked my service advisor about it and she told me this......

Hi Nic,



All 2004’s and newer have the world flush transmission fluid which will not need to be serviced until 100,000 miles or over.

You should go to my dealership although I see your live in Texas. Woodfield Lexus in Illinois recommends that I change my trannsmission and rear differential fluids atleast every 30k miles. I did bring up the fact that Lexus engineers say that it's lifetime and there is no interval for this in owners manual. The tech went on to tell me that he has spoke to Lexus engineers about this as when they do drain the tranny and rear differential fluids, the fluid that comes out is very dark and smells horribly after just 35-40k miles. The tech said that they put lifetime fluids in there due to the demands of current consumers. He said that consumers today want a car that requires as little maintenance as possible. The Lexus engineer did tell the tech the they do not advise against changing the fluids as it will only help with the longetivity of the parts. He also told me that the term "lifetime" is good for about 100k miles. After 70k miles Lexus does not need to worry about warranty anymore so it falls on the consumer. The Lexus tech did tell me that I can hold off alittle longer for the transmission fluid but he absolutely would not hold off longer than 30k for the rear differential.

The dealers know this should be done - they won't give you any Chit about it. My Dealer recommends at 30, 60, 90 intervals - if you are planning to keep the vehicle.........

That stuff smells horribly when it is fresh! The "very dark" color is more thought provoking though.

I don't know people. It's hard for me to just agree with changing the trans fluid every 30k miles or so when I consider that the interval of "lifetime" is coming from the same mfgrs that have been very relectant to extending oil change intervals even though so many here are already doing that. Of course the dealerships wopuld love to take your money every 30k miles for trans fluid changes.

I want to be clear though. I'm not for or against changing trans fluids. I just need to see more data and come to my own conclusion about this which I haven't been able to do. Until then, I'm just going with the mfgrs. spec.

It was my understanding that the fluid can not be fully flushed by pump in the IS250/350. It requires a full dismantling of the unit.

Nope not true. If that were the case nobody would ever do it. Many people do it in there garage but most just go to the dealer. It's tricky because you need to pump the fluid in at the same rate it's coming out.

Mr. Raider - I'm not sure about a "full dismantling", but they would definitely need to drop the transmission pan to access the transmission pump pick-up (inlet) to connect their machine. In all honesty, I haven't looked to see how difficult the trans pan in our car is to access, so maybe that is where the "dismantling" description comes in.

Another shop I used to work in simply disconnected the transmission cooler lines for the fresh supply and old fluid returns. Not as effective as an inlet pump, but definitely a quicker/cleaner procedure.

One last thing to note: during both types of procedures the vehicle is running, so the transmission pump is determining the rate. Not an external pump/flush machine.