My 2006 (actually purchased in Aug. 2005) only has 26K on it. Does the transmission fluid deteriorate based on time or miles?
7 years is a very long time for dirty trans fluid to sit in the trans. Acid will build up. Its very cheap insurance to replace it. That includes the Engine and the Inverter coolant also.
All, Here is some real data on Toyota Type WS ATF performance in my 2004 Prius over the first 240k miles of it's use. Testing of ATF samples was done by R&G Labs of Tampa FL on Virgin ATF and at each 60k miles of use when the ATF was drained and refilled. Several things should be noted: The wear metals build up quickly in the first few miles to unreasonably high levels and then the rate of metallic wear decreases to a low level. There is a high silicon content in the original factory ATF which seems to be due to factory sealants. Both of these factors suggest that an early ATF drain and refill is advisable - I suggest doing one at 30k miles. The Viscosity tests indicate that the Type WS ATF lubrication properties are weakening by 60k miles. So I suggest a drain and refill each 60k miles thereafter if you want to take good care of your Prius transmission. It can be done DIY or, if you want, should only cost about $100 at a Toyota dealer JeffD
The fluid is usually not replaced during that pump replacement done under that TSB. They just clamp each hose off and swap the pump in. Then top off the small amount they lose.
