I have been doing a lot of research on Lexus IS transmissions. A lot of threads say it is sealed and therefore impossible to change the fluid inside the transmission. Even the maintennance schedule says it never needs to be changed. For some of us who like having cars for the long haul its probably makes us think twice about the life of the fluid. I want to clarify what I have learnt about the transmission over the last few weeks.
1. The fluid is meant to last 100,000km (WS ATF fluid)(Stated by several Dealers and Ex mechanics from Lexus)
2. The transmission fluid can be changed by dropping the pan and refilling the lost fluid through the side of the transmission.
About 1.5 litres is contained within the pan.
3. The fluid can and should be changed as part of regular maintennance. It takes about 8 litres for a full flush.
4. There is a mesh filter in the transmission which should be changed and an o-ring which should also be replaced.
5. Using a special pump machine at a transmission service centre [NOT THE DEALER OP!] for about 100 bucks depending where you go, you can get the whole transmission fluid and filter all replaced.
6. You can purchase the WS ATF FLUID 4L cannisters and FILTER AND O-RING from Lexus Parts.
WHY DOES LEXUS SAY ITS LIFETIME?
Once the car is out of warranty, your fluid will lose its viscosity and protective properties. Heat and metal shavings from normal use will or even excessive towing will cause the transmission fluid to be damaged over time. When people purchase cars runnings costs play a major factor. What Lexus hopes is that the car will be sold before the 100,000km mark. This way transmission maintennace is out of the picture hence a lower running cost [making it more appealing for buyers]. At this stage the car is out of warranty. Without replacing the fluid the car will begin to have rough changes and hesitation whilst changing gears. Eventually you will need a new transmission. This will cost about 7000 dollars from the dealer+labour. It's up to you what you want to believe but I have changed all my fluid and filter and the hesitation between gears and low idling rpm problem was all solved. Also the large amount of heat coming from the transmission was also gone. It's up to you what you want to do but for those who want to keep their cars running fine for the long run I recommend you change your fluid before you cause more damage than good when your transmission is too old.
I just wanted to place an end to all this confusion with lexus IS transmissions!!! Cheers.